On Tue, Jun 29, 2021 at 6:14 AM Christian Brauner <christian.brauner@xxxxxxxxxx> wrote: > > On Wed, Jun 23, 2021 at 12:28:22PM -0700, Suren Baghdasaryan wrote: > > In modern systems it's not unusual to have a system component monitoring > > memory conditions of the system and tasked with keeping system memory > > pressure under control. One way to accomplish that is to kill > > non-essential processes to free up memory for more important ones. > > Examples of this are Facebook's OOM killer daemon called oomd and > > Android's low memory killer daemon called lmkd. > > For such system component it's important to be able to free memory > > quickly and efficiently. Unfortunately the time process takes to free > > up its memory after receiving a SIGKILL might vary based on the state > > of the process (uninterruptible sleep), size and OPP level of the core > > the process is running. A mechanism to free resources of the target > > process in a more predictable way would improve system's ability to > > control its memory pressure. > > Introduce process_reap system call that reclaims memory of a dying process > > from the context of the caller. This way the memory in freed in a more > > controllable way with CPU affinity and priority of the caller. The workload > > of freeing the memory will also be charged to the caller. > > The operation is allowed only on a dying process. > > > > Previously I proposed a number of alternatives to accomplish this: > > - https://lore.kernel.org/patchwork/patch/1060407 extending > > pidfd_send_signal to allow memory reaping using oom_reaper thread; > > - https://lore.kernel.org/patchwork/patch/1338196 extending > > pidfd_send_signal to reap memory of the target process synchronously from > > the context of the caller; > > - https://lore.kernel.org/patchwork/patch/1344419/ to add MADV_DONTNEED > > support for process_madvise implementing synchronous memory reaping. > > > > The end of the last discussion culminated with suggestion to introduce a > > dedicated system call (https://lore.kernel.org/patchwork/patch/1344418/#1553875) > > The reasoning was that the new variant of process_madvise > > a) does not work on an address range > > b) is destructive > > c) doesn't share much code at all with the rest of process_madvise > > From the userspace point of view it was awkward and inconvenient to provide > > memory range for this operation that operates on the entire address space. > > Using special flags or address values to specify the entire address space > > was too hacky. > > > > The API is as follows, > > > > int process_reap(int pidfd, unsigned int flags); > > > > DESCRIPTION > > The process_reap() system call is used to free the memory of a > > dying process. > > > > The pidfd selects the process referred to by the PID file > > descriptor. > > (See pidofd_open(2) for further information) > > > > The flags argument is reserved for future use; currently, this > > argument must be specified as 0. > > > > RETURN VALUE > > On success, process_reap() returns 0. On error, -1 is returned > > and errno is set to indicate the error. > > > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > > --- > > arch/alpha/kernel/syscalls/syscall.tbl | 1 + > > arch/arm/tools/syscall.tbl | 1 + > > arch/arm64/include/asm/unistd.h | 2 +- > > arch/arm64/include/asm/unistd32.h | 2 + > > arch/ia64/kernel/syscalls/syscall.tbl | 1 + > > arch/m68k/kernel/syscalls/syscall.tbl | 1 + > > arch/microblaze/kernel/syscalls/syscall.tbl | 1 + > > arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + > > arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + > > arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + > > arch/parisc/kernel/syscalls/syscall.tbl | 1 + > > arch/powerpc/kernel/syscalls/syscall.tbl | 1 + > > arch/s390/kernel/syscalls/syscall.tbl | 1 + > > arch/sh/kernel/syscalls/syscall.tbl | 1 + > > arch/sparc/kernel/syscalls/syscall.tbl | 1 + > > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > > arch/xtensa/kernel/syscalls/syscall.tbl | 1 + > > include/linux/syscalls.h | 1 + > > include/uapi/asm-generic/unistd.h | 4 +- > > kernel/sys_ni.c | 1 + > > mm/oom_kill.c | 50 +++++++++++++++++++++ > > 22 files changed, 74 insertions(+), 2 deletions(-) > > > > diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl > > index 3000a2e8ee21..14b9e81d2fc4 100644 > > --- a/arch/alpha/kernel/syscalls/syscall.tbl > > +++ b/arch/alpha/kernel/syscalls/syscall.tbl > > @@ -486,3 +486,4 @@ > > 554 common landlock_create_ruleset sys_landlock_create_ruleset > > 555 common landlock_add_rule sys_landlock_add_rule > > 556 common landlock_restrict_self sys_landlock_restrict_self > > +557 common process_reap sys_process_reap > > diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl > > index 28e03b5fec00..889b78d0f63f 100644 > > --- a/arch/arm/tools/syscall.tbl > > +++ b/arch/arm/tools/syscall.tbl > > @@ -460,3 +460,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h > > index 727bfc3be99b..fb7a0be2f3d9 100644 > > --- a/arch/arm64/include/asm/unistd.h > > +++ b/arch/arm64/include/asm/unistd.h > > @@ -38,7 +38,7 @@ > > #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) > > #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) > > > > -#define __NR_compat_syscalls 447 > > +#define __NR_compat_syscalls 448 > > #endif > > > > #define __ARCH_WANT_SYS_CLONE > > diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h > > index 5dab69d2c22b..80593454173e 100644 > > --- a/arch/arm64/include/asm/unistd32.h > > +++ b/arch/arm64/include/asm/unistd32.h > > @@ -900,6 +900,8 @@ __SYSCALL(__NR_landlock_create_ruleset, sys_landlock_create_ruleset) > > __SYSCALL(__NR_landlock_add_rule, sys_landlock_add_rule) > > #define __NR_landlock_restrict_self 446 > > __SYSCALL(__NR_landlock_restrict_self, sys_landlock_restrict_self) > > +#define __NR_process_reap 447 > > +__SYSCALL(__NR_process_reap, sys_process_reap) > > > > /* > > * Please add new compat syscalls above this comment and update > > diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl > > index bb11fe4c875a..6c94feedf086 100644 > > --- a/arch/ia64/kernel/syscalls/syscall.tbl > > +++ b/arch/ia64/kernel/syscalls/syscall.tbl > > @@ -367,3 +367,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl > > index 79c2d24c89dd..e80a7fa55696 100644 > > --- a/arch/m68k/kernel/syscalls/syscall.tbl > > +++ b/arch/m68k/kernel/syscalls/syscall.tbl > > @@ -446,3 +446,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl > > index b11395a20c20..511b2bd61fc1 100644 > > --- a/arch/microblaze/kernel/syscalls/syscall.tbl > > +++ b/arch/microblaze/kernel/syscalls/syscall.tbl > > @@ -452,3 +452,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl > > index 9220909526f9..1775704c6a24 100644 > > --- a/arch/mips/kernel/syscalls/syscall_n32.tbl > > +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl > > @@ -385,3 +385,4 @@ > > 444 n32 landlock_create_ruleset sys_landlock_create_ruleset > > 445 n32 landlock_add_rule sys_landlock_add_rule > > 446 n32 landlock_restrict_self sys_landlock_restrict_self > > +447 n32 process_reap sys_process_reap > > diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl > > index 9cd1c34f31b5..d769daca3f79 100644 > > --- a/arch/mips/kernel/syscalls/syscall_n64.tbl > > +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl > > @@ -361,3 +361,4 @@ > > 444 n64 landlock_create_ruleset sys_landlock_create_ruleset > > 445 n64 landlock_add_rule sys_landlock_add_rule > > 446 n64 landlock_restrict_self sys_landlock_restrict_self > > +447 n64 process_reap sys_process_reap > > diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl > > index d560c467a8c6..1bd2fc056677 100644 > > --- a/arch/mips/kernel/syscalls/syscall_o32.tbl > > +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl > > @@ -434,3 +434,4 @@ > > 444 o32 landlock_create_ruleset sys_landlock_create_ruleset > > 445 o32 landlock_add_rule sys_landlock_add_rule > > 446 o32 landlock_restrict_self sys_landlock_restrict_self > > +447 o32 process_reap sys_process_reap > > diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl > > index aabc37f8cae3..0012561ca557 100644 > > --- a/arch/parisc/kernel/syscalls/syscall.tbl > > +++ b/arch/parisc/kernel/syscalls/syscall.tbl > > @@ -444,3 +444,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl > > index 8f052ff4058c..89cbcc732b18 100644 > > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > > @@ -526,3 +526,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl > > index 0690263df1dd..7ebd4d809b5e 100644 > > --- a/arch/s390/kernel/syscalls/syscall.tbl > > +++ b/arch/s390/kernel/syscalls/syscall.tbl > > @@ -449,3 +449,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap sys_process_reap > > diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl > > index 0b91499ebdcf..178fd47b372e 100644 > > --- a/arch/sh/kernel/syscalls/syscall.tbl > > +++ b/arch/sh/kernel/syscalls/syscall.tbl > > @@ -449,3 +449,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl > > index e34cc30ef22c..faee121b7ae2 100644 > > --- a/arch/sparc/kernel/syscalls/syscall.tbl > > +++ b/arch/sparc/kernel/syscalls/syscall.tbl > > @@ -492,3 +492,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > > index 4bbc267fb36b..cbe070de9884 100644 > > --- a/arch/x86/entry/syscalls/syscall_32.tbl > > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > > @@ -451,3 +451,4 @@ > > 444 i386 landlock_create_ruleset sys_landlock_create_ruleset > > 445 i386 landlock_add_rule sys_landlock_add_rule > > 446 i386 landlock_restrict_self sys_landlock_restrict_self > > +447 i386 process_reap sys_process_reap > > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > > index ce18119ea0d0..e6765646731b 100644 > > --- a/arch/x86/entry/syscalls/syscall_64.tbl > > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > > @@ -368,6 +368,7 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > > > # > > # Due to a historical design error, certain syscalls are numbered differently > > diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl > > index fd2f30227d96..f0e9dbee1a5b 100644 > > --- a/arch/xtensa/kernel/syscalls/syscall.tbl > > +++ b/arch/xtensa/kernel/syscalls/syscall.tbl > > @@ -417,3 +417,4 @@ > > 444 common landlock_create_ruleset sys_landlock_create_ruleset > > 445 common landlock_add_rule sys_landlock_add_rule > > 446 common landlock_restrict_self sys_landlock_restrict_self > > +447 common process_reap sys_process_reap > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > > index 050511e8f1f8..b6659e09bf0d 100644 > > --- a/include/linux/syscalls.h > > +++ b/include/linux/syscalls.h > > @@ -915,6 +915,7 @@ asmlinkage long sys_mincore(unsigned long start, size_t len, > > asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); > > asmlinkage long sys_process_madvise(int pidfd, const struct iovec __user *vec, > > size_t vlen, int behavior, unsigned int flags); > > +asmlinkage long sys_process_reap(int pidfd, unsigned int flags); > > asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, > > unsigned long prot, unsigned long pgoff, > > unsigned long flags); > > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > > index d2a942086fcb..b3bf57b928af 100644 > > --- a/include/uapi/asm-generic/unistd.h > > +++ b/include/uapi/asm-generic/unistd.h > > @@ -871,9 +871,11 @@ __SYSCALL(__NR_landlock_create_ruleset, sys_landlock_create_ruleset) > > __SYSCALL(__NR_landlock_add_rule, sys_landlock_add_rule) > > #define __NR_landlock_restrict_self 446 > > __SYSCALL(__NR_landlock_restrict_self, sys_landlock_restrict_self) > > +#define __NR_process_reap 447 > > +__SYSCALL(__NR_process_reap, sys_process_reap) > > > > #undef __NR_syscalls > > -#define __NR_syscalls 447 > > +#define __NR_syscalls 448 > > > > /* > > * 32 bit systems traditionally used different > > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > > index 0ea8128468c3..56eb7c9f8356 100644 > > --- a/kernel/sys_ni.c > > +++ b/kernel/sys_ni.c > > @@ -289,6 +289,7 @@ COND_SYSCALL(munlockall); > > COND_SYSCALL(mincore); > > COND_SYSCALL(madvise); > > COND_SYSCALL(process_madvise); > > +COND_SYSCALL(process_reap); > > COND_SYSCALL(remap_file_pages); > > COND_SYSCALL(mbind); > > COND_SYSCALL_COMPAT(mbind); > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index eefd3f5fde46..0f85a0442fa5 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -28,6 +28,7 @@ > > #include <linux/sched/task.h> > > #include <linux/sched/debug.h> > > #include <linux/swap.h> > > +#include <linux/syscalls.h> > > #include <linux/timex.h> > > #include <linux/jiffies.h> > > #include <linux/cpuset.h> > > @@ -1141,3 +1142,52 @@ void pagefault_out_of_memory(void) > > out_of_memory(&oc); > > mutex_unlock(&oom_lock); > > } > > + > > +SYSCALL_DEFINE2(process_reap, int, pidfd, unsigned int, flags) > > Hey Suren, > > Wouldn't > - process_memory_reap() > - process_reap_memory() > - process_mreap() > be better names? Hi Christian, I'm open to other names, whichever sounds better. From the list process_reap_memory() sounds best to me but I'm open to others as well. > > > +{ > > + struct pid *pid; > > + struct task_struct *task; > > + struct mm_struct *mm = NULL; > > + unsigned int f_flags; > > + long ret = 0; > > + > > + if (flags != 0) > > + return -EINVAL; > > + > > + pid = pidfd_get_pid(pidfd, &f_flags); > > + if (IS_ERR(pid)) > > + return PTR_ERR(pid); > > + > > + task = get_pid_task(pid, PIDTYPE_PID); > > + if (!task) { > > + ret = -ESRCH; > > + goto put_pid; > > + } > > You have a similar pattern in process_madvise(): > > pid = pidfd_get_pid(pidfd, &f_flags); > if (IS_ERR(pid)) { > ret = PTR_ERR(pid); > goto free_iov; > } > > task = get_pid_task(pid, PIDTYPE_PID); > if (!task) { > ret = -ESRCH; > goto put_pid; > } > > I'd suggest you add a tiny helper to kernel/pid.c and call it in both > places. Agree. I'll post the new rev next week to give some more time for reviews of this version. Thanks! > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@xxxxxxxxxxx. >
