Re: [PATCH v3 1/2] mm/page_idle: Add per-pid idle page tracking using virtual indexing
From: Joel Fernandes <hidden>
Date: 2019-07-30 13:06:55
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linux-doc, linux-fsdevel, linux-mm, lkml
On Fri, Jul 26, 2019 at 11:23 AM Joel Fernandes (Google) [off-list ref] wrote:
The page_idle tracking feature currently requires looking up the pagemap for a process followed by interacting with /sys/kernel/mm/page_idle. Looking up PFN from pagemap in Android devices is not supported by unprivileged process and requires SYS_ADMIN and gives 0 for the PFN. This patch adds support to directly interact with page_idle tracking at the PID level by introducing a /proc/<pid>/page_idle file. It follows the exact same semantics as the global /sys/kernel/mm/page_idle, but now looking up PFN through pagemap is not needed since the interface uses virtual frame numbers, and at the same time also does not require SYS_ADMIN. In Android, we are using this for the heap profiler (heapprofd) which profiles and pin points code paths which allocates and leaves memory idle for long periods of time. This method solves the security issue with userspace learning the PFN, and while at it is also shown to yield better results than the pagemap lookup, the theory being that the window where the address space can change is reduced by eliminating the intermediate pagemap look up stage. In virtual address indexing, the process's mmap_sem is held for the duration of the access. Signed-off-by: Joel Fernandes (Google) <redacted> --- v2->v3: Fixed a bug where I was doing a kfree that is not needed due to not needing to do GFP_ATOMIC allocations. v1->v2: Mark swap ptes as idle (Minchan) Avoid need for GFP_ATOMIC (Andrew) Get rid of idle_page_list lock by moving list to stack
I believe all suggestions have been addressed. Do these look good now? thanks, - Joel
quoted hunk ↗ jump to hunk
Internal review -> v1: Fixes from Suren. Corrections to change log, docs (Florian, Sandeep) fs/proc/base.c | 3 + fs/proc/internal.h | 1 + fs/proc/task_mmu.c | 57 +++++++ include/linux/page_idle.h | 4 + mm/page_idle.c | 340 +++++++++++++++++++++++++++++++++----- 5 files changed, 360 insertions(+), 45 deletions(-)diff --git a/fs/proc/base.c b/fs/proc/base.c index 77eb628ecc7f..a58dd74606e9 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c@@ -3021,6 +3021,9 @@ 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),