Re: [PATCH v3 2/3] Introduce GIT_MMAP_LIMIT to allow testing expected mmap size
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Aug 21, 2014, 22:26 UTC
- Message-ID
- <xmqq1ts9qy24.fsf@gitster.dls.corp.google.com>
- In-Reply-To
- <1408637110-15669-3-git-send-email-prohaska@zib.de>
Steffen Prohaska <prohaska@zib.de> writes:
Show 9 quoted lines
> Similar to testing expectations about malloc with GIT_ALLOC_LIMIT (see > commit d41489), it can be useful to test expectations about mmap. > > This introduces a new environment variable GIT_MMAP_LIMIT to limit the > largest allowed mmap length (in KB). xmmap() is modified to check the > limit. Together with GIT_ALLOC_LIMIT tests can now easily confirm > expectations about memory consumption. > > GIT_ALLOC_LIMIT will be used in the next commit to test that data will
I smell the need for s/ALLOC/MMAP/ here, but perhaps you did mean ALLOC (I won't know until I check 3/3 ;-)
Show 21 quoted lines
> be streamed to an external filter without mmaping the entire file.
>
> [commit d41489]: d41489a6424308dc9a0409bc2f6845aa08bd4f7d Add more large
> blob test cases
>
> Signed-off-by: Steffen Prohaska <prohaska@zib.de>
> ---
> sha1_file.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/sha1_file.c b/sha1_file.c
> index 00c07f2..88d64c0 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -663,10 +663,25 @@ void release_pack_memory(size_t need)
> ; /* nothing */
> }
>
> +static void mmap_limit_check(size_t length)
> +{
> + static int limit = -1;Perhaps you want ssize_t here? I see mmap() as a tool to handle a lot more data than a single malloc() typically would ;-) so previous mistakes by other people would not be a good excuse.
Show 20 quoted lines
> + if (limit == -1) {
> + const char *env = getenv("GIT_MMAP_LIMIT");
> + limit = env ? atoi(env) * 1024 : 0;
> + }
> + if (limit && length > limit)
> + die("attempting to mmap %"PRIuMAX" over limit %d",
> + (intmax_t)length, limit);
> +}
> +
> void *xmmap(void *start, size_t length,
> int prot, int flags, int fd, off_t offset)
> {
> - void *ret = mmap(start, length, prot, flags, fd, offset);
> + void *ret;
> +
> + mmap_limit_check(length);
> + ret = mmap(start, length, prot, flags, fd, offset);
> if (ret == MAP_FAILED) {
> if (!length)
> return NULL;