Date: Mon, 29 Jun 2015 13:14:12 +0000 From: "emaste (Ed Maste)" <phabric-noreply@FreeBSD.org> To: freebsd-toolchain@freebsd.org Subject: [Differential] [Updated, 26 lines] D2933: Significantly speed up ar(1) on UFS file systems Message-ID: <a222931c107847e855b5d47d28ef7204@localhost.localdomain> In-Reply-To: <differential-rev-PHID-DREV-hkid5hylfsbts6yuvnph-req@FreeBSD.org>
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[-- Attachment #1 --] emaste updated this revision to Diff 6543. emaste added a comment. This revision now requires review to proceed. - give full path to file with comment explaining the deadlock avoidance - avoid confusing page mask manipulation and just touch the last byte explicitly CHANGES SINCE LAST UPDATE https://reviews.freebsd.org/D2933?vs=6524&id=6543 REVISION DETAIL https://reviews.freebsd.org/D2933 AFFECTED FILES usr.bin/ar/write.c CHANGE DETAILS diff --git a/usr.bin/ar/write.c b/usr.bin/ar/write.c --- a/usr.bin/ar/write.c +++ b/usr.bin/ar/write.c @@ -41,6 +41,7 @@ #include <stdlib.h> #include <string.h> #include <sysexits.h> +#include <unistd.h> #include "ar.h" @@ -61,6 +62,7 @@ static void free_obj(struct bsdar *bsdar, struct ar_obj *obj); static void insert_obj(struct bsdar *bsdar, struct ar_obj *obj, struct ar_obj *pos); +static void prefault_buffer(const char *buf, size_t s); static void read_objs(struct bsdar *bsdar, const char *archive, int checkargv); static void write_archive(struct bsdar *bsdar, char mode); @@ -551,11 +553,35 @@ } /* + * Fault in the buffer prior to writing as a workaround for poor performance + * due to interaction with kernel fs deadlock avoidance code. See the comment + * above vn_io_fault_doio() in sys/kern/vfs_vnops.c for details of the issue. + */ +static void +prefault_buffer(const char *buf, size_t s) +{ + volatile const char *p; + size_t page_size; + + if (s == 0) + return; + page_size = sysconf(_SC_PAGESIZE); + for (p = buf; p < buf + s; p += page_size) + *p; + /* + * Ensure we touch the last page as well, in case the buffer is not + * page-aligned. + */ + *(volatile const char *)(buf + s - 1); +} + +/* * Wrapper for archive_write_data(). */ static void write_data(struct bsdar *bsdar, struct archive *a, const void *buf, size_t s) { + prefault_buffer(buf, s); if (archive_write_data(a, buf, s) != (ssize_t)s) bsdar_errc(bsdar, EX_SOFTWARE, 0, "%s", archive_error_string(a)); EMAIL PREFERENCES https://reviews.freebsd.org/settings/panel/emailpreferences/ To: emaste, kib, eadler Cc: kib, freebsd-toolchain-list, dim, davide [-- Attachment #2 --] diff --git a/usr.bin/ar/write.c b/usr.bin/ar/write.c --- a/usr.bin/ar/write.c +++ b/usr.bin/ar/write.c @@ -41,6 +41,7 @@ #include <stdlib.h> #include <string.h> #include <sysexits.h> +#include <unistd.h> #include "ar.h" @@ -61,6 +62,7 @@ static void free_obj(struct bsdar *bsdar, struct ar_obj *obj); static void insert_obj(struct bsdar *bsdar, struct ar_obj *obj, struct ar_obj *pos); +static void prefault_buffer(const char *buf, size_t s); static void read_objs(struct bsdar *bsdar, const char *archive, int checkargv); static void write_archive(struct bsdar *bsdar, char mode); @@ -551,11 +553,35 @@ } /* + * Fault in the buffer prior to writing as a workaround for poor performance + * due to interaction with kernel fs deadlock avoidance code. See the comment + * above vn_io_fault_doio() in sys/kern/vfs_vnops.c for details of the issue. + */ +static void +prefault_buffer(const char *buf, size_t s) +{ + volatile const char *p; + size_t page_size; + + if (s == 0) + return; + page_size = sysconf(_SC_PAGESIZE); + for (p = buf; p < buf + s; p += page_size) + *p; + /* + * Ensure we touch the last page as well, in case the buffer is not + * page-aligned. + */ + *(volatile const char *)(buf + s - 1); +} + +/* * Wrapper for archive_write_data(). */ static void write_data(struct bsdar *bsdar, struct archive *a, const void *buf, size_t s) { + prefault_buffer(buf, s); if (archive_write_data(a, buf, s) != (ssize_t)s) bsdar_errc(bsdar, EX_SOFTWARE, 0, "%s", archive_error_string(a));home | help
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