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BTW: where did you see that stat is called before each write? can you point out the code or function that does this? I might want to look into the source code to see whether we can improve it. Thanks, Xin On 10/8/05, Xin Zhao <uszhaoxin@gmail.com> wrote: > I think the stat might be one reason. cuz when I do 'nfsstat', I > noticed that "getattr" and "setattr" are executed about 40000 times > while other operations are executed for less than 10000 times. That > gave me a feeling that some optimization can be considered to reduce > the getattr and setattr requests. > > async and sync options affect write performance on large files more > significantly. But decompress kernel involves a lot of small files. > Because nfs will force data sync to disk before file close. async and > sync do not behave quite different. > > Anyone has exeprience with NFS4? I don't know whether it improves in this parts > > Xin > > On 10/8/05, Willy Tarreau <willy@w.ods.org> wrote: > > Hi, > > > > On Sat, Oct 08, 2005 at 01:59:48AM -0400, Lee Revell wrote: > > > On Sat, 2005-10-08 at 00:39 -0400, Xin Zhao wrote: > > > > I noticed that when doing large file copy or linux kernel compilation > > > > in a NFS direcotry, the performance is not bad compared to local disk > > > > filesystem such as ext2. However, if I do linux kernel tarball > > > > decompression on a NFS directory, the performance is much worse than > > > > local disk filesystem (over 3 times slower). Anybody know the reason? > > > > > > Because NFS requires all writes to be synchronous by default, and > > > uncompressing the kernel is the most write intensive of those three > > > operations. Mount with the async option and the performance should be > > > closer to a local disk. Obviously this is more dangerous. > > > > I don't agree with you, Lee. My NFS is mounted with async by default, > > and what takes the most time when extracting a kernel archive is that > > tar does a stat() on every file before writing it. And THAT stat() > > prevents writes from being buffered. A better solution might be to > > process several files in parallel (multi-process/multi-thread). > > Perhaps a project for a new tar ? > > > > Just for a test, I tried extracting multiple files in parallel. The > > method is completely crappy, but I could saturate my NFS server this > > way : > > > > $ tar ztf /tmp/linux-2.6.9.tar.gz >/tmp/file-list > > $ sed -n '1~4p' < /tmp/file-list >/tmp/file-list1 > > $ sed -n '2~4p' < /tmp/file-list >/tmp/file-list2 > > $ sed -n '3~4p' < /tmp/file-list >/tmp/file-list3 > > $ sed -n '4~4p' < /tmp/file-list >/tmp/file-list4 > > > > $ tar zxf /tmp/linux-2.6.9.tar.gz -T /tmp/file-list1 & tar zxf /tmp/linux-2.6.9.tar.gz -T /tmp/file-list2 & tar zxf /tmp/linux-2.6.9.tar.gz -T /tmp/file-list3 & tar zxf /tmp/linux-2.6.9.tar.gz -T /tmp/file-list4 & wait > > > > OK, it finally took more time, although the server was saturated (maybe > > it crawled under seeks at the end, I did not check). This may constitute > > a starting point for people having more time to research in this area. > > > > > Lee > > > > Cheers, > > Willy > > > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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