Hi glibc maintainers, I have a performance "problem" which I do not understand. If I allocate a memory buffer of 1 GB (aligned to pagesize) and do a memset(), then this takes 1.1 seconds. If I copy this buffer to another one using memcpy(), it takes about 1.7 seconds. But if I use memmove() or bcopy() it takes only 0.7s and 0.5s:
memset took 1.100437 seconds -> 930.54 MB/s memcpy took 1.366200 seconds -> 749.52 MB/s bcopy took 0.703371 seconds -> 1.42 GB/s memmove took 0.545014 seconds -> 1.83 GB/s I tried to look at the source code, but got lost somewhere. For me it looks like they are all using the same code. So I do not understand why memcpy() is so slow. Do you have any ideas, hints, pointers, ...? >From the C source it looks identically, but there are also some assembler codes in the source tree and finally I am not sure which code is used for which function. I am using wheezy, libc6:amd64 2.13-35 amd64 but the squeeze version shows the same behaviour. Maybe there is some room to optimize memcpy()? Best regards Dirk -- +----------------------------------------------------------------------+ | Dr. Dirk Geschke / Plankensteinweg 61 / 85435 Erding | | Telefon: 08122-559448 / Mobil: 0176-96906350 / Fax: 08122-9818106 | | [email protected] / [email protected] / [email protected] | +----------------------------------------------------------------------+ -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
