Andi Kleen wrote:
> On Friday 28 December 2007 01:10:51 [email protected] wrote:
>> x86_64 provides an optimized way to determine the local per cpu area
>> offset through the pda and determines the base by accessing a remote
>> pda.
>
> And? The rationale for this patch seems to be incomplete.
>
> As far as I can figure out you're replacing an optimized percpu
> implementation which a dumber generic one. Which needs
> at least some description why.
The specific intent for the next wave of changes coming are to reduce
the impact of having a large NR_CPUS count on smaller systems and to
minimize memory traffic between nodes. This patchset addresses the
per_cpu data areas in preparation to cpu_alloc changes to compact the
PERCPU area, remove the various per_cpu data offset and pointer arrays,
and speed up calculating the per_cpu data offset.
Since those changes have a bigger impact it was felt that we should
prepare the groundwork before hand. It also has the benefit of
merging one more of the i386 and x86_64 headers.
> If the generic one is now as good or better than the
> specific one that might be ok, but that should be somewhere
> in the description.
I could gather some performance data, though the effect will be
larger as later changes are made.
> Also for such changes .text size comparisons before/after
> are a good idea.
x86_64-defconfig:
pre-percpu post-percpu
225 .altinstr_replacemen +0 .altinstr_replacemen
1195 .altinstructions +0 .altinstructions
716104 .bss +0 .bss
58300 .comment +0 .comment
16 .con_initcall.init +0 .con_initcall.init
415816 .data +0 .data
178688 .data.cacheline_alig +0 .data.cacheline_alig
8192 .data.init_task +0 .data.init_task
4096 .data.page_aligned +0 .data.page_aligned
27008 .data.percpu +0 .data.percpu
43904 .data.read_mostly +0 .data.read_mostly
4 .data_nosave +0 .data_nosave
5097 .exit.text +0 .exit.text
138384 .init.data +0 .init.data
133 .init.ramfs +0 .init.ramfs
3192 .init.setup +0 .init.setup
159373 .init.text +3 .init.text
2296 .initcall.init +0 .initcall.init
8 .jiffies +0 .jiffies
4512 .pci_fixup +0 .pci_fixup
1411137 .rodata +8 .rodata
35400 .smp_locks +0 .smp_locks
3629056 .text +48 .text
3368 .vdso +0 .vdso
4 .vgetcpu_mode +0 .vgetcpu_mode
218 .vsyscall_0 +0 .vsyscall_0
52 .vsyscall_1 +0 .vsyscall_1
91 .vsyscall_2 +0 .vsyscall_2
8 .vsyscall_3 +0 .vsyscall_3
54 .vsyscall_fn +0 .vsyscall_fn
80 .vsyscall_gtod_data +0 .vsyscall_gtod_data
39144 __bug_table +0 __bug_table
16320 __ex_table +0 __ex_table
44592 __ksymtab +0 __ksymtab
15200 __ksymtab_gpl +0 __ksymtab_gpl
48 __ksymtab_gpl_future +0 __ksymtab_gpl_future
87756 __ksymtab_strings +0 __ksymtab_strings
32 __ksymtab_unused_gpl +0 __ksymtab_unused_gpl
8280 __param +0 __param
7057383 Total +59 Total
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
