On Wed, 2013-05-29 at 18:56 +0200, Andi Kleen wrote: > On Wed, May 29, 2013 at 12:18:09PM -0400, Simo Sorce wrote: > > On Wed, 2013-05-29 at 11:55 -0400, Waiman Long wrote: > > > > > My patch set consists of 2 different changes. The first one is to avoid > > > taking the d_lock lock when updating the reference count in the > > > dentries. This particular change also benefit some other workloads that > > > are filesystem intensive. One particular example is the short workload > > > in the AIM7 benchmark. One of the job type in the short workload is > > > "misc_rtns_1" which calls security functions like getpwnam(), > > > getpwuid(), getgrgid() a couple of times. These functions open the > > > /etc/passwd or /etc/group files, read their content and close the files. > > > It is the intensive open/read/close sequence from multiple threads that > > > is causing 80%+ contention in the d_lock on a system with large number > > > of cores. > > > > To be honest a workload base on /etc/passwd or /etc/group is completely > > artificial, in actual usage, if you really have such access you use > > nscd or sssd with their shared memory caches to completely remove most > > of the file access. > > I don't fully agree at this point. A lot of things can be tuned away, > but in practice we want things to perform well out of the box without > needing all kinds of magic tuning that only Phrase seem cut mid-sentence ? > Also this is just normal file access, nothing special about it. > It simply has to scale. For all kinds of workloads. > > And it does, just d_path messes it up. Well there are reasonable workloads and artificial ones, I am just warning not to use 'that' specific test as a good indicator, if you have other reasonable workloads that show a similar flow feel free to bring it up. > > I have no beef on the rest but repeated access to Nsswitch information > > is not something you need to optimize at the file system layer and > > should not be brought up as a point in favor. > > This is about repeated access to arbitrary files. Ok. I do not want to start a discussion on this, I just pointed out the specific point was not really a good example hopefully there are others that justify the patchset. Simo. -- Simo Sorce * Red Hat, Inc * New York -- To unsubscribe from this list: send the line "unsubscribe autofs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
