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    SubjectRe: [PATCH] Allow increasing the buffer-head per-CPU LRU size
    On Mon, 7 Jul 2014 18:30:03 +0200 Andi Kleen <andi@firstfloor.org> wrote:

    > > diff --git a/fs/Kconfig b/fs/Kconfig
    > > index c229f82..c08844c 100644
    > > --- a/fs/Kconfig
    > > +++ b/fs/Kconfig
    > > @@ -268,4 +268,13 @@ endif # NETWORK_FILESYSTEMS
    > > source "fs/nls/Kconfig"
    > > source "fs/dlm/Kconfig"
    > >
    > > +config BH_LRU_SIZE
    > > + int
    > > + range 8 64
    > > + default "16"
    >
    > So who sets it then?
    >
    > You need it for ext4 and quota right? So this combination
    > should set it at least. Something like (unested)
    >
    > It would be also good to audit or test other file systems if they need the
    > same if that's possible.
    >
    > config BH_LARGE_LRU
    > bool
    > depends on (EXT4_FS && QUOTA)
    >
    > config BH_LRU_SIZE
    > ....
    > default "16" if BH_LARGE_LRU
    > default "8" if !BH_LARGE_LRU

    Can anyone demonstrate why we shouldn't just do

    --- a/fs/buffer.c~a
    +++ a/fs/buffer.c
    @@ -1258,7 +1258,7 @@ static struct buffer_head *__bread_slow(
    * a local interrupt disable for that.
    */

    -#define BH_LRU_SIZE 8
    +#define BH_LRU_SIZE 16

    struct bh_lru {
    struct buffer_head *bhs[BH_LRU_SIZE];
    _


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