This will be similar to /sys/kernel/mm/page_idle/bitmap documented in Documentation/admin-guide/mm/idle_page_tracking.rst, however indexed by process virtual address. When using the global PFN indexed idle bitmap, we find 2 kind of overheads: - to track a task's working set, Brendan Gregg end up writing wss-v1 for small tasks and wss-v2 for large tasks: https://github.com/brendangregg/wss That's because VAs may point to random PAs throughout the physical address space. So we either query /proc/pid/pagemap first and access the lots of random PFNs (with lots of syscalls) in the bitmap, or write+read the whole system idle bitmap beforehand. - page table walking by PFN has much more overheads than to walk a page table in its natural order: - rmap queries - more locking - random memory reads/writes This interface provides a cheap path for the majority non-shared mapping pages. To walk 1TB memory of 4k active pages, it costs 2s vs 15s system time to scan the per-task/global idle bitmaps. Which means ~7x speedup. The gap will be enlarged if consider - the extra /proc/pid/pagemap walk - natural page table walks can skip the whole 512 PTEs if PMD is idle OTOH, the per-task idle bitmap is not suitable in some situations: - not accurate for shared pages - don't work with non-mapped file pages - don't perform well for sparse page tables (pointed out by Huang Ying) So it's more about complementing the existing global idle bitmap. CC: Huang Ying <ying.huang@xxxxxxxxx> CC: Brendan Gregg <bgregg@xxxxxxxxxxx> Signed-off-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> --- fs/proc/base.c | 2 ++ fs/proc/internal.h | 1 + fs/proc/task_mmu.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 66 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index aaffc0c30216..d81322b5b8d2 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2942,6 +2942,7 @@ static const struct pid_entry tgid_base_stuff[] = { REG("smaps", S_IRUGO, proc_pid_smaps_operations), REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations), REG("pagemap", S_IRUSR, proc_pagemap_operations), + REG("idle_bitmap", S_IRUSR|S_IWUSR, proc_mm_idle_operations), #endif #ifdef CONFIG_SECURITY DIR("attr", S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations), @@ -3327,6 +3328,7 @@ static const struct pid_entry tid_base_stuff[] = { REG("smaps", S_IRUGO, proc_tid_smaps_operations), REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations), REG("pagemap", S_IRUSR, proc_pagemap_operations), + REG("idle_bitmap", S_IRUSR|S_IWUSR, proc_mm_idle_operations), #endif #ifdef CONFIG_SECURITY DIR("attr", S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations), diff --git a/fs/proc/internal.h b/fs/proc/internal.h index da3dbfa09e79..732a502acc27 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -305,6 +305,7 @@ extern const struct file_operations proc_pid_smaps_rollup_operations; extern const struct file_operations proc_tid_smaps_operations; extern const struct file_operations proc_clear_refs_operations; extern const struct file_operations proc_pagemap_operations; +extern const struct file_operations proc_mm_idle_operations; extern unsigned long task_vsize(struct mm_struct *); extern unsigned long task_statm(struct mm_struct *, diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index dfd73a4616ce..376406a9cf45 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1564,6 +1564,69 @@ const struct file_operations proc_pagemap_operations = { .open = pagemap_open, .release = pagemap_release, }; + +/* will be filled when kvm_ept_idle module loads */ +struct file_operations proc_ept_idle_operations = { +}; +EXPORT_SYMBOL_GPL(proc_ept_idle_operations); + +static ssize_t mm_idle_read(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + struct task_struct *task = file->private_data; + ssize_t ret = -ESRCH; + + // TODO: implement mm_walk for normal tasks + + if (task_kvm(task)) { + if (proc_ept_idle_operations.read) + return proc_ept_idle_operations.read(file, buf, count, ppos); + } + + return ret; +} + + +static int mm_idle_open(struct inode *inode, struct file *file) +{ + struct task_struct *task = get_proc_task(inode); + + if (!task) + return -ESRCH; + + file->private_data = task; + + if (task_kvm(task)) { + if (proc_ept_idle_operations.open) + return proc_ept_idle_operations.open(inode, file); + } + + return 0; +} + +static int mm_idle_release(struct inode *inode, struct file *file) +{ + struct task_struct *task = file->private_data; + + if (!task) + return 0; + + if (task_kvm(task)) { + if (proc_ept_idle_operations.release) + return proc_ept_idle_operations.release(inode, file); + } + + put_task_struct(task); + return 0; +} + +const struct file_operations proc_mm_idle_operations = { + .llseek = mem_lseek, /* borrow this */ + .read = mm_idle_read, + .open = mm_idle_open, + .release = mm_idle_release, +}; + #endif /* CONFIG_PROC_PAGE_MONITOR */ #ifdef CONFIG_NUMA -- 2.15.0
