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Home » Mailing list archives » linux-kernel » 2007 » December » 11

[PATCH] RCU : move three variables to __read_mostly to save space

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From: Eric Dumazet <dada1@...>
To: Andrew Morton <akpm@...>
Cc: Dipankar Sarma <dipankar@...>, Linux kernel <linux-kernel@...>
Subject: [PATCH] RCU : move three variables to __read_mostly to save space
Date: Tuesday, December 11, 2007 - 12:50 am

I noticed this vmlinux layout on i686 (where CONFIG_X86_L1_CACHE_SHIFT = 7) :

c06cdab4 d pid_caches_lh
c06cdb00 d qlowmark
c06cdb04 d qhimark
c06cdb08 d blimit
c06cdb80 d rcu_ctrlblk
c06cdc80 d rcu_bh_ctrlblk

This means that qlowmark, qhimark and blimit use a whole 128 bytes cache line. 
Linker is not smart enough for us.

Moving these three variables to read_mostly section saves 116 (128-12) bytes.

# size vmlinux vmlinux.before_patch
    text    data     bss     dec     hex filename
6343966  490818  630784 7465568  71ea60 vmlinux
6343966  490930  630784 7465680  71ead0 vmlinux.before_patch

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
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[PATCH] RCU : move three variables to __read_mostly to save ..., Eric Dumazet, (Tue Dec 11, 12:50 am)

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