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Message-ID: <CACOAw_zhZ0OgT-KCBmD_H6_U=CZCNY44D-ojH2AZah2cbAvdAQ@mail.gmail.com>
Date: Fri, 12 Mar 2021 22:56:13 +0900
From: Daeho Jeong <daeho43@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [PATCH v4] f2fs: add sysfs nodes to get runtime compression stat
Thanks for suggesting me sysfs_emit().
For atomic values, actually, those are needed for writer part, not reader.
+#define add_compr_block_stat(inode, blocks) \
+ do { \
+ struct f2fs_sb_info *sbi = F2FS_I_SB(inode); \
+ int diff = F2FS_I(inode)->i_cluster_size - blocks; \
+ atomic64_add(blocks, &sbi->compr_written_block); \
+ atomic64_add(diff, &sbi->compr_saved_block); \
+ } while (0)
I needed a protection here, because they might be updated in the race condition.
2021년 3월 12일 (금) 오후 9:39, Greg KH <gregkh@...uxfoundation.org>님이 작성:
>
> On Fri, Mar 12, 2021 at 09:25:31PM +0900, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@...gle.com>
> >
> > I've added new sysfs nodes to show runtime compression stat since mount.
> > compr_written_block - show the block count written after compression
> > compr_saved_block - show the saved block count with compression
> > compr_new_inode - show the count of inode newly enabled for compression
> >
> > Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> > ---
> > v2: thanks to kernel test robot <lkp@...el.com>, fixed compile issue
> > related to kernel config
> > v3: changed sysfs nodes' names and made them runtime stat, not
> > persistent on disk
> > v4: changed sysfs nodes' desctiption
> > ---
> > Documentation/ABI/testing/sysfs-fs-f2fs | 24 ++++++++++
> > fs/f2fs/compress.c | 1 +
> > fs/f2fs/f2fs.h | 19 ++++++++
> > fs/f2fs/super.c | 7 +++
> > fs/f2fs/sysfs.c | 58 +++++++++++++++++++++++++
> > 5 files changed, 109 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> > index cbeac1bebe2f..ddd4bd6116fc 100644
> > --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> > +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> > @@ -409,3 +409,27 @@ Description: Give a way to change checkpoint merge daemon's io priority.
> > I/O priority "3". We can select the class between "rt" and "be",
> > and set the I/O priority within valid range of it. "," delimiter
> > is necessary in between I/O class and priority number.
> > +
> > +What: /sys/fs/f2fs/<disk>/compr_written_block
> > +Date: March 2021
> > +Contact: "Daeho Jeong" <daehojeong@...gle.com>
> > +Description: Show the block count written after compression since mount. Note
> > + that when the compressed blocks are deleted, this count doesn't
> > + decrease. If you write "0" here, you can initialize
> > + compr_written_block and compr_saved_block to "0".
> > +
> > +What: /sys/fs/f2fs/<disk>/compr_saved_block
> > +Date: March 2021
> > +Contact: "Daeho Jeong" <daehojeong@...gle.com>
> > +Description: Show the saved block count with compression since mount. Note
> > + that when the compressed blocks are deleted, this count doesn't
> > + decrease. If you write "0" here, you can initialize
> > + compr_written_block and compr_saved_block to "0".
> > +
> > +What: /sys/fs/f2fs/<disk>/compr_new_inode
> > +Date: March 2021
> > +Contact: "Daeho Jeong" <daehojeong@...gle.com>
> > +Description: Show the count of inode newly enabled for compression since mount.
> > + Note that when the compression is disabled for the files, this count
> > + doesn't decrease. If you write "0" here, you can initialize
> > + compr_new_inode to "0".
> > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > index 77fa342de38f..3c9d797dbdd6 100644
> > --- a/fs/f2fs/compress.c
> > +++ b/fs/f2fs/compress.c
> > @@ -1353,6 +1353,7 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
> > if (fio.compr_blocks)
> > f2fs_i_compr_blocks_update(inode, fio.compr_blocks - 1, false);
> > f2fs_i_compr_blocks_update(inode, cc->nr_cpages, true);
> > + add_compr_block_stat(inode, cc->nr_cpages);
> >
> > set_inode_flag(cc->inode, FI_APPEND_WRITE);
> > if (cc->cluster_idx == 0)
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index e2d302ae3a46..2c989f8caf05 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1623,6 +1623,11 @@ struct f2fs_sb_info {
> > #ifdef CONFIG_F2FS_FS_COMPRESSION
> > struct kmem_cache *page_array_slab; /* page array entry */
> > unsigned int page_array_slab_size; /* default page array slab size */
> > +
> > + /* For runtime compression statistics */
> > + atomic64_t compr_written_block;
> > + atomic64_t compr_saved_block;
> > + atomic_t compr_new_inode;
>
> Why do you need these to be atomic? What requires this?
>
> > +#ifdef CONFIG_F2FS_FS_COMPRESSION
> > + if (!strcmp(a->attr.name, "compr_written_block")) {
> > + u64 bcount;
> > + int len;
> > +
> > + bcount = atomic64_read(&sbi->compr_written_block);
> > +
> > + len = scnprintf(buf, PAGE_SIZE, "%llu\n", bcount);
>
> Please use sysfs_emit() for new sysfs entries like these. Makes it much
> simpler.
>
> And look, you really do not need an atomic value as this is just a
> random number you are sending to userspace that could be stale the
> minute you read from it.
>
> Please just use a normal u64 and save the cpu sync for stuff like this.
>
> thanks,
>
> greg k-h
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