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Date: Fri, 07 Nov 2008 21:33:49 -0500 From: Masami Hiramatsu <mhiramat@...hat.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Ananth N Mavinakayanahalli <ananth@...ibm.com>, Jim Keniston <jkenisto@...ibm.com>, David Miller <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>, maneesh@...ibm.com, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Srinivasa Ds <srinivasa@...ibm.com> Subject: Re: [PATCH] kprobe: increase kprobe_hash_table size Andrew Morton wrote: >> I agree that there may be many opinions about what is the best suited size. >> Why I chose 512 was that I thought the table (byte) size was less than or >> equal 4096 even on 64-bit arch. > > Well... > > text data bss dec hex filename > 7036 744 9380 17160 4308 kernel/kprobes.o > 7048 744 73892 81684 13f14 kernel/kprobes.o > > That's 64 kbytes more memory. It will be kretprobe_table_locks[] which > is hurting here, due to the ____cacheline_aligned. Oops! It's really bad. > I expected CONFIG_X86_VSMP=y to make this far worse, but fortunately > that only affects ____cacheline_internodealigned_in_smp. > > btw, that array wastes a ton of memory on uniprocessor builds. Using > ____cacheline_aligned_in_smp should fix that. > > Please always check these thigns with /usr/bin/size. I see. I'll check that and try to find the best way... > btw2, could/should kprobe_table[] and kretprobe_inst_table[] be > aggregated into kretprobe_table_locks[]? That would save some memory > and might save some cache misses as well? Indeed, thank you for good idea. > Anyway, enough pos-facto code review. Is this change which you're > proposing worth increasing kernel memory usage by 64k? Not really. Hmm, I have to investigate more on this problem. Thanks a lot. -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@...hat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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