RE: [PATCH v2] Prefer sysconf(_SC_OPEN_MAX) over getrlimit(RLIMIT_NOFILE,...)
> From: Junio C Hamano [mailto:gits...@pobox.com]
> Sent: Friday, August 24, 2012 6:44 PM
> To: Joachim Schmitz
> Cc: git@vger.kernel.org
> Subject: Re: [PATCH v2] Prefer sysconf(_SC_OPEN_MAX) over
> getrlimit(RLIMIT_NOFILE,...)
>
> "Joachim Schmitz" writes:
>
> > Signed-off-by: Joachim Schmitz
> > ---
> > As discussed now as a small helper function rather than #ifdef/#endif in
> > the primary flow of the code.
> > And hopefully without having screwed up whitespace and line breaks
>
> The formatting looks fine.
>
> Perhaps I am being overly paranoid, but I would prefer not to change
> things for people who have been using getrlimit(). For them, if
> they also have sysconf(_SC_OPEN_MAX), your code _ought to_ work, but
> if it does not work for whatever reason (perhaps some platforms
> claim to have both, but getrlimit() works and sysconf(_SC_OPEN_MAX)
> is broken), it will given them an unnecessary regression.
Sounds reasonable, so reasonable that I wonder why I didn't have that idea ;-)
> So how about doing it this way instead?
>
> -- >8 --
> Subject: sha1_file.c: introduce get_max_fd_limit() helper
>
> Not all platforms have getrlimit(), but there are other ways to see
> the maximum number of files that a process can have open. If
> getrlimit() is unavailable, fall back to sysconf(_SC_OPEN_MAX) if
> available, and use OPEN_MAX from .
>
> Signed-off-by: Joachim Schmitz
> Signed-off-by: Junio C Hamano
> ---
> sha1_file.c | 26 +++---
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git c/sha1_file.c w/sha1_file.c
> index af5cfbd..9152974 100644
> --- c/sha1_file.c
> +++ w/sha1_file.c
> @@ -731,6 +731,24 @@ void free_pack_by_name(const char *pack_name)
> }
> }
>
> +static unsigned int get_max_fd_limit(void)
> +{
> +#ifdef RLIMIT_NOFILE
> + struct rlimit lim;
> +
> + if (getrlimit(RLIMIT_NOFILE, &lim))
> + die_errno("cannot get RLIMIT_NOFILE");
> +
> + return lim.rlim_cur;
> +#elif defined(_SC_OPEN_MAX)
> + return sysconf(_SC_OPEN_MAX);
> +#elif defined(OPEN_MAX)
> + return OPEN_MAX;
> +#else
> + return 1; /* see the caller ;-) */
> +#endif
> +}
> +
> /*
> * Do not call this directly as this leaks p->pack_fd on error return;
> * call open_packed_git() instead.
> @@ -747,13 +765,7 @@ static int open_packed_git_1(struct packed_git *p)
> return error("packfile %s index unavailable", p->pack_name);
>
> if (!pack_max_fds) {
> - struct rlimit lim;
> - unsigned int max_fds;
> -
> - if (getrlimit(RLIMIT_NOFILE, &lim))
> - die_errno("cannot get RLIMIT_NOFILE");
> -
> - max_fds = lim.rlim_cur;
> + unsigned int max_fds = get_max_fd_limit();
>
> /* Save 3 for stdin/stdout/stderr, 22 for work */
> if (25 < max_fds)
Looks good to me.
Stupid newbie question: how would I revert my commit to my clone, to then add
(and test) this one?
Bye, Jojo
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Re: [PATCH v2] Prefer sysconf(_SC_OPEN_MAX) over getrlimit(RLIMIT_NOFILE,...)
"Joachim Schmitz" writes:
> Signed-off-by: Joachim Schmitz
> ---
> As discussed now as a small helper function rather than #ifdef/#endif in the
> primary flow of the code.
> And hopefully without having screwed up whitespace and line breaks
The formatting looks fine.
Perhaps I am being overly paranoid, but I would prefer not to change
things for people who have been using getrlimit(). For them, if
they also have sysconf(_SC_OPEN_MAX), your code _ought to_ work, but
if it does not work for whatever reason (perhaps some platforms
claim to have both, but getrlimit() works and sysconf(_SC_OPEN_MAX)
is broken), it will given them an unnecessary regression.
So how about doing it this way instead?
-- >8 --
Subject: sha1_file.c: introduce get_max_fd_limit() helper
Not all platforms have getrlimit(), but there are other ways to see
the maximum number of files that a process can have open. If
getrlimit() is unavailable, fall back to sysconf(_SC_OPEN_MAX) if
available, and use OPEN_MAX from .
Signed-off-by: Joachim Schmitz
Signed-off-by: Junio C Hamano
---
sha1_file.c | 26 +++---
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git c/sha1_file.c w/sha1_file.c
index af5cfbd..9152974 100644
--- c/sha1_file.c
+++ w/sha1_file.c
@@ -731,6 +731,24 @@ void free_pack_by_name(const char *pack_name)
}
}
+static unsigned int get_max_fd_limit(void)
+{
+#ifdef RLIMIT_NOFILE
+ struct rlimit lim;
+
+ if (getrlimit(RLIMIT_NOFILE, &lim))
+ die_errno("cannot get RLIMIT_NOFILE");
+
+ return lim.rlim_cur;
+#elif defined(_SC_OPEN_MAX)
+ return sysconf(_SC_OPEN_MAX);
+#elif defined(OPEN_MAX)
+ return OPEN_MAX;
+#else
+ return 1; /* see the caller ;-) */
+#endif
+}
+
/*
* Do not call this directly as this leaks p->pack_fd on error return;
* call open_packed_git() instead.
@@ -747,13 +765,7 @@ static int open_packed_git_1(struct packed_git *p)
return error("packfile %s index unavailable", p->pack_name);
if (!pack_max_fds) {
- struct rlimit lim;
- unsigned int max_fds;
-
- if (getrlimit(RLIMIT_NOFILE, &lim))
- die_errno("cannot get RLIMIT_NOFILE");
-
- max_fds = lim.rlim_cur;
+ unsigned int max_fds = get_max_fd_limit();
/* Save 3 for stdin/stdout/stderr, 22 for work */
if (25 < max_fds)
--
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[PATCH v2] Prefer sysconf(_SC_OPEN_MAX) over getrlimit(RLIMIT_NOFILE,...)
Signed-off-by: Joachim Schmitz
---
As discussed now as a small helper function rather than #ifdef/#endif in the
primary flow of the code.
And hopefully without having screwed up whitespace and line breaks
sha1_file.c | 22 +++---
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/sha1_file.c b/sha1_file.c
index af5cfbd..427f9e6 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -731,6 +731,20 @@ void free_pack_by_name(const char *pack_name)
}
}
+static unsigned int get_max_fd_limit(void)
+{
+#ifdef _SC_OPEN_MAX
+ return sysconf(_SC_OPEN_MAX);
+#else
+ struct rlimit lim;
+
+ if (getrlimit(RLIMIT_NOFILE, &lim))
+ die_errno("cannot get RLIMIT_NOFILE");
+
+ return lim.rlim_cur;
+#endif
+}
+
/*
* Do not call this directly as this leaks p->pack_fd on error return;
* call open_packed_git() instead.
@@ -747,13 +761,7 @@ static int open_packed_git_1(struct packed_git *p)
return error("packfile %s index unavailable", p->pack_name);
if (!pack_max_fds) {
- struct rlimit lim;
- unsigned int max_fds;
-
- if (getrlimit(RLIMIT_NOFILE, &lim))
- die_errno("cannot get RLIMIT_NOFILE");
-
- max_fds = lim.rlim_cur;
+ unsigned int max_fds = get_max_fd_limit();
/* Save 3 for stdin/stdout/stderr, 22 for work */
if (25 < max_fds)
--
1.7.12
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