xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

x86: optimize lock prefix switching to run less frequently

Browse Source 
On VMs implemented using JITs that cache translated code changing the lock
prefixes is a quite costly operation that forces the JIT to throw away and
retranslate a lot of code.

Previously a SMP kernel would rewrite the locks once for each CPU which
is quite unnecessary. This patch changes the code to never switch at boot in
 the normal case (SMP kernel booting with >1 CPU) or only once for SMP kernel
on UP.

This makes a significant difference in boot up performance on AMD SimNow!
Also I expect it to be a little faster on native systems too because a smp
switch does a lot of text_poke()s which each synchronize the pipeline.

v1->v2: Rename max_cpus
v1->v2: Fix off by one in UP check (Thomas Gleixner)

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andi Kleen
2008-01-30 13:33:17 +01:00
committed by Ingo Molnar
parent 7517527891
commit ca74a6f84e
3 changed files with 24 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/smp.h
View File

@@ -78,6 +78,8 @@ int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait);
*/
void smp_prepare_boot_cpu(void);
extern unsigned int setup_max_cpus;
#else /* !SMP */
/*