Messages in this thread | | | From | "Wichert, Gerhard" <> | Subject | AW: [bigmem-patch] 4GB with Linux on IA32 | Date | Fri, 20 Aug 1999 15:37:25 +0200 |
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> -----Ursprüngliche Nachricht----- > Von: Wichert, Gerhard > Gesendet am: Mittwoch, 18. August 1999 10:43 > An: 'Matthew Wilcox' > Cc: 'linux-kernel@vger.rutgers.edu'; 'linux-mm@kvack.org' > Betreff: AW: [bigmem-patch] 4GB with Linux on IA32 > > > This is a resend to x-linux-kernel@vger.rutgers.edu
> > > -----Ursprüngliche Nachricht----- > > > Von: Matthew Wilcox [mailto:Matthew.Wilcox@genedata.com] > > > Gesendet am: Dienstag, 17. August 1999 16:32 > > > An: Wichert, Gerhard > > > Cc: linux-kernel@vger.rutgers.edu; linux-mm@kvack.org > > > Betreff: Re: [bigmem-patch] 4GB with Linux on IA32 > > > > > > On Mon, Aug 16, 1999 at 06:29:30PM +0200, Andrea Arcangeli wrote: > > > > Performance degradation: > > > > > > > > Close to zero. > > So, here are some additional nubers based on this little > worst case bench from Andrea Arcangeli. > > #define SIZE (700*1024*1024) > > main() > { > unsigned long start, stop; > int i; > char *buf = (char *)malloc(SIZE); > > if (!buf) > perror("malloc"); > > i = 0; > > __asm__ __volatile__ ("rdtsc" :"=a" (start)::"edx"); > for (; i < SIZE; i += 4096, buf += 4096) > *(int *)buf = 0; > > __asm__ __volatile__ ("rdtsc" :"=a" (stop)::"edx"); > > printf("ticks %ul\n", stop-start); > } > > This bench shows the overhead for establishing the temporary > kernel mapping for the bigmem page. > > Linux-2.3.13: > run 1 > ticks 1313001994l > run 2 > ticks 1310999320l > run 3 > ticks 1309894069l > run 4 > ticks 1313788902l > run 5 > ticks 1308360521l > > Linux-2.3.13 with bigmem support: > run 1 > ticks 1331834802l > run 2 > ticks 1332486766l > run 3 > ticks 1332231641l > run 4 > ticks 1332125591l > run 5 > ticks 1333419476l > > This shows that we get only approx. 2% overhead in the worst > case. In real-world applications you won't probably see any > performance degradation. > > Gerhard >
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