Re: [Patch] Delete sysfs_dirent.s_count, saving ~100kB on my system

From: Adam J. Richter (adam_at_yggdrasil.com)
Date: 12/02/04

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    Date:	Wed, 1 Dec 2004 18:59:02 -0800
To: akpm@osdl.org, chrisw@osdl.org

    Chris Wright wrote:
    >* Andrew Morton (akpm@osdl.org) wrote:
    >> That's all well and good, but sysfs_new_dirent() should be using a
    >> standalone slab cache for allocating sysfs_dirent instances. That way, we
    >> use 36 bytes for each one rather than 64.

    >Reasonable, here's a patch (lightly tested). [...]

            Great. That way 32-bit architectures should be able to
    benefit from some another shrink of sysfs_dirent that I'd like
    to do, and it will also help 64-bit architectures (where sysfs_dirent
    is still larger than 32 bytes even with my change).

            I applied Chris's patch on top of my own (which still
    saves about 14kB on my machine and shrinks the source code by 11
    lines) and I am running it now. It looks fine to me, although I
    haven't looked into making a separate slab cache before. I guess
    it's okay that there is no alignment requirement on it for now,
    as there are a lot of sysfs_dirent structure and more every day,
    and programs that would access these structures frequently would
    also probably cause access to a lot of them at the same time (by
    scanning the sysfs tree), so inter-processor cache line contention
    might be offset by the more efficient utilization of the processor's
    cache.

            Chris's patch file applied without conflict (there was a
    one line offset in fs/sysfs/sysfs.h), so it should be easy to
    integrate both patches. Please let me know if there is anything
    further I should or can do to help make that happen, as I'd like
    to have my fs/sysfs tree in sync before trying to unpin the
    struct dirent and struct inode for sysfs directories, as I
    expect that to be a more complex patch (and unpin hundreds of kbytes).

                        __ ______________
    Adam J. Richter \ /
    adam@yggdrasil.com | g g d r a s i l
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