[Differential] [Closed] D2933: Significantly speed up ar(1) on UFS file systems

[emaste (Ed Maste)]

This revision was automatically updated to reflect the committed changes.
Closed by commit rS284928: speed up ar(1) on UFS file systems (authored by emaste).

CHANGED PRIOR TO COMMIT
  https://reviews.freebsd.org/D2933?vs=6543&id=6545#toc

REPOSITORY
  rS FreeBSD src repository

CHANGES SINCE LAST UPDATE
  https://reviews.freebsd.org/D2933?vs=6543&id=6545

REVISION DETAIL
  https://reviews.freebsd.org/D2933

AFFECTED FILES
  head/usr.bin/ar/write.c

CHANGE DETAILS
  diff --git a/head/usr.bin/ar/write.c b/head/usr.bin/ar/write.c
  --- a/head/usr.bin/ar/write.c
  +++ b/head/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));

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To: emaste, eadler, kib
Cc: kib, freebsd-toolchain-list, dim, davide
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