Date: Wed, 17 Jan 2018 21:54:34 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-standards@FreeBSD.org Subject: [Bug 218622] libc/gen/telldir [hack-n-PATCH] performance limited to O(n) vs file count, O(n^2) against samba ls workload Message-ID: <bug-218622-15-OFpjyIbJWj@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-218622-15@https.bugs.freebsd.org/bugzilla/> References: <bug-218622-15@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D218622 Alan Somers <asomers@FreeBSD.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |asomers@FreeBSD.org --- Comment #7 from Alan Somers <asomers@FreeBSD.org> --- FWIW I have further improved upon mav's solution with r326640. Now, telldi= r is O(1) in both time and space on 64-bit systems. r326640 | asomers | 2017-12-06 15:06:48 -0700 (Wed, 06 Dec 2017) | 22 lines Optimize telldir(3) Currently each call to telldir() requires a malloc and adds an entry to a linked list which must be traversed on future telldir(), seekdir(), closedir(), and readdir() calls. Applications that call telldir() for every directory entry incur O(n^2) behavior in readdir() and O(n) in telldir() and closedir(). This optimization eliminates the malloc() and linked list in most cases by packing the relevant information into a single long. On 64-bit architectures msdosfs, NFS, tmpfs, UFS, and ZFS can all use the packed representation. On 32-bit architectures msdosfs, NFS, and UFS can use the packed representation, but ZFS and tmpfs can only use it for about the first 128 files per directory. Memory savings is about 50 bytes per telldir(3) call. Speedup for telldir()-heavy directory traversals is about 20-30x for one million files per directory. Reviewed by: kib, mav, mckusick MFC after: 3 weeks Sponsored by: Spectra Logic Corp Differential Revision: https://reviews.freebsd.org/D13385 --=20 You are receiving this mail because: You are the assignee for the bug.=
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