On Wed, Jun 29, 2022 at 01:43:11PM -0700, Kalesh Singh wrote:
On Wed, Jun 29, 2022 at 5:23 AM Brian Foster bfoster@redhat.com wrote:
On Tue, Jun 28, 2022 at 03:38:02PM -0700, Kalesh Singh wrote:
On Tue, Jun 28, 2022 at 4:54 AM Brian Foster bfoster@redhat.com wrote:
On Thu, Jun 23, 2022 at 03:06:06PM -0700, Kalesh Singh wrote:
To be able to account the amount of memory a process is keeping pinned by open file descriptors add a 'size' field to fdinfo output.
dmabufs fds already expose a 'size' field for this reason, remove this and make it a common field for all fds. This allows tracking of other types of memory (e.g. memfd and ashmem in Android).
Signed-off-by: Kalesh Singh kaleshsingh@google.com Reviewed-by: Christian König christian.koenig@amd.com
Changes in v2:
- Add Christian's Reviewed-by
Changes from rfc:
- Split adding 'size' and 'path' into a separate patches, per Christian
- Split fdinfo seq_printf into separate lines, per Christian
- Fix indentation (use tabs) in documentaion, per Randy
Documentation/filesystems/proc.rst | 12 ++++++++++-- drivers/dma-buf/dma-buf.c | 1 - fs/proc/fd.c | 9 +++++---- 3 files changed, 15 insertions(+), 7 deletions(-)
...
Also not sure if it matters that much for your use case, but something worth noting at least with shmem is that one can do something like:
# cat /proc/meminfo | grep Shmem: Shmem: 764 kB # xfs_io -fc "falloc -k 0 10m" ./file # ls -alh file -rw-------. 1 root root 0 Jun 28 07:22 file # stat file File: file Size: 0 Blocks: 20480 IO Block: 4096 regular empty file # cat /proc/meminfo | grep Shmem: Shmem: 11004 kB
... where the resulting memory usage isn't reflected in i_size (but is is in i_blocks/bytes).
I tried a similar experiment a few times, but I don't see the same results. In my case, there is not any change in shmem. IIUC the fallocate is allocating the disk space not shared memory.
Sorry, it was implied in my previous test was that I was running against tmpfs. So regardless of fs, the fallocate keep_size semantics shown in both cases is as expected: the underlying blocks are allocated and the inode size is unchanged.
What wasn't totally clear to me when I read this patch was 1. whether tmpfs refers to Shmem and 2. whether tmpfs allowed this sort of operation. The test above seems to confirm both, however, right? E.g., a more detailed example:
# mount | grep /tmp tmpfs on /tmp type tmpfs (rw,nosuid,nodev,seclabel,nr_inodes=1048576,inode64) # cat /proc/meminfo | grep Shmem: Shmem: 5300 kB # xfs_io -fc "falloc -k 0 1g" /tmp/file # stat /tmp/file File: /tmp/file Size: 0 Blocks: 2097152 IO Block: 4096 regular empty file Device: 22h/34d Inode: 45 Links: 1 Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Context: unconfined_u:object_r:user_tmp_t:s0 Access: 2022-06-29 08:04:01.301307154 -0400 Modify: 2022-06-29 08:04:01.301307154 -0400 Change: 2022-06-29 08:04:01.451312834 -0400 Birth: 2022-06-29 08:04:01.301307154 -0400 # cat /proc/meminfo | grep Shmem: Shmem: 1053876 kB # rm -f /tmp/file # cat /proc/meminfo | grep Shmem: Shmem: 5300 kB
So clearly this impacts Shmem.. was your test run against tmpfs or some other (disk based) fs?
Hi Brian,
Thanks for clarifying. My issue was tmpfs not mounted at /tmp in my system:
==> meminfo.start <== Shmem: 572 kB ==> meminfo.stop <== Shmem: 51688 kB
Ok, makes sense.
FWIW, I don't have any objection to exposing inode size if it's commonly useful information. My feedback was more just an fyi that i_size doesn't necessarily reflect underlying space consumption (whether it's memory or disk space) in more generic cases, because it sounds like that is really what you're after here. The opposite example to the above would be something like an 'xfs_io -fc "truncate 1t" /tmp/file', which shows a 1TB inode size with zero additional shmem usage.
From these cases, it seems the more generic way to do this is by calculating the actual size consumed using the blocks. (i_blocks * 512). So in the latter example 'xfs_io -fc "truncate 1t" /tmp/file' the size consumed would be zero. Let me know if it sounds ok to you and I can repost the updated version.
That sounds a bit more useful to me if you're interested in space usage, or at least I don't have a better idea for you. ;)
One thing to note is that I'm not sure whether all fs' use i_blocks reliably. E.g., XFS populates stat->blocks via a separate block counter in the XFS specific inode structure (see xfs_vn_getattr()). A bunch of other fs' seem to touch it so perhaps that is just an outlier. You could consider fixing that up, perhaps make a ->getattr() call to avoid it, or just use the field directly if it's useful enough as is and there are no other objections. Something to think about anyways..
Brian
Thanks, Kalesh
Brian
cat /proc/meminfo > meminfo.start xfs_io -fc "falloc -k 0 50m" ./xfs_file cat /proc/meminfo > meminfo.stop tail -n +1 meminfo.st* | grep -i '==|Shmem:'
==> meminfo.start <== Shmem: 484 kB ==> meminfo.stop <== Shmem: 484 kB
ls -lh xfs_file -rw------- 1 root root 0 Jun 28 15:12 xfs_file
stat xfs_file File: xfs_file Size: 0 Blocks: 102400 IO Block: 4096 regular empty file
Thanks, Kalesh
Brian
/* show_fd_locks() never deferences files so a stale value is safe */ show_fd_locks(m, file, files);-- 2.37.0.rc0.161.g10f37bed90-goog
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