Messages in this thread | | | Date | Thu, 4 Jun 2015 08:58:13 -0700 | From | Josh Triplett <> | Subject | Re: [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone |
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On Thu, Jun 04, 2015 at 12:07:31PM +0200, Denys Vlasenko wrote: > On 06/03/2015 06:38 PM, Josh Triplett wrote: > > On Wed, Jun 03, 2015 at 03:58:50PM +0200, Denys Vlasenko wrote: > >> Really swap arguments #4 and #5 in stub32_clone instead of "optimizing" > >> it into a move. > >> > >> Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a little bit > >> more expensive than MOV. But a cycle or two on an expensive syscall like > >> clone() is way below noise floor, and this optimization is simply not worth > >> the obfuscation of logic. > > [...] > >> This is a resend. > >> > >> There was a patch by Josh Triplett > >> "x86: Opt into HAVE_COPY_THREAD_TLS, for both 32-bit and 64-bit" > >> sent on May 11, > >> which does the same thing as part of a bigger cleanup. > >> He was supportive of this patch because of comments. > >> He will simply have to drop one hunk from his patch. > > > > Strictly speaking, nothing needs this until clone starts paying > > attention to its tls argument, which only happens in my cleanup series > > that includes this change. So what's the purpose of driving this patch > > separately? > > You wanted my comments in this patch to go in: > > On 04/22/2015 07:10 PM, Josh Triplett wrote: > > I do think my two-patch HAVE_COPY_THREAD_TLS series should go in fixing > > this, but I'd like to see the final version of Denys' comment added on > > top of it (with an update to the type and name of the tls argument to > > match the changes to sys_clone). > > If your patch will go in first, I'll send a patch adding only the comment. > > Since for now your patch did not make it yet, I'm submitting > a patch which adds both a comment and the insn change.
Ah, I see.
My two-patch series is currently sitting in -mm; would you consider providing a version of the patch that adds the comment for Andrew to apply on top of those?
- Josh Triplett
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