Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 22 Nov 2006 13:36:18 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] dont insert pipe dentries into dentry_hashtable. |
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On Wed, 22 Nov 2006 18:48:41 +0100 Eric Dumazet <dada1@cosmosbay.com> wrote:
> We currently insert pipe dentries into the global dentry hashtable. > This is *suboptimal* because there is currently no way these entries can be > used for a lookup(). (/proc/xxx/fd/xxx uses a different mechanism). Inserting > them in dentry hashtable slow dcache lookups. > > > To let __dpath() still work correctly (ie not adding a " (deleted)") after > dentry name, we do : > > - Right after d_alloc(), pretend they are hashed by clearing the > DCACHE_UNHASHED bit. > > - Call d_instantiate() instead of d_add() : dentry is not inserted in hash > table. > > __dpath() & friends work as intended during dentry lifetime. > > - At dismantle time, once dput() must clear the dentry, setting again > DCACHE_UNHASHED bit inside the custom d_delete() function provided by pipe > code, so that dput() can just kill_it. > > This patch, combined with the next one (avoid RCU for never hashed dentries) > reduced time of { pipe(p); close(p[0]); close(p[1]);} on my UP machine > (1.6GHz Pentium-M) from 3.23 us to 2.86 us > (But this patch does not depend on other patches, only bench results)
The DCACHE_UNHASHED games seem hacky.
Would it be cleaner to define a new dentry.d_flags bit which can be used to indicate that this is a hashing-not-needed dentry, and to handle that over in dcache.c? - 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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