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? > +{ > + 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.
