Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1427856
| From | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [Y2038] [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros |
| Date | 2016-06-21 17:10 +0200 |
| Message-ID | <rMvtn-7tu-3@gated-at.bofh.it> (permalink) |
| References | <rLVgd-11C-1@gated-at.bofh.it> <rMbO1-3aM-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Monday, June 20, 2016 11:03:01 AM CEST you wrote:
> On Sun, Jun 19, 2016 at 5:26 PM, Deepa Dinamani <deepa.kernel@gmail.com> wrote:
> > The series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros.
> Gcc handles 8-byte structure returns (on most architectures) by
> returning them as two 32-bit registers (%edx:%eax on x86). But once it
> is timespec64, that will no longer be the case, and the calling
> convention will end up using a pointer to the local stack instead.
I guess we already have that today, as the implementation of
current_fs_time() is
static inline struct timespec64 tk_xtime(struct timekeeper *tk)
{
struct timespec64 ts;
ts.tv_sec = tk->xtime_sec;
ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
return ts;
}
extern struct timespec64 current_kernel_time64(void);
struct timespec64 current_kernel_time64(void)
{
struct timekeeper *tk = &tk_core.timekeeper;
struct timespec64 now;
unsigned long seq;
do {
seq = read_seqcount_begin(&tk_core.seq);
now = tk_xtime(tk);
} while (read_seqcount_retry(&tk_core.seq, seq));
return now;
}
static inline struct timespec current_kernel_time(void)
{
struct timespec64 now = current_kernel_time64();
return timespec64_to_timespec(now);
}
extern struct timespec current_fs_time(struct super_block *sb);
struct timespec current_fs_time(struct super_block *sb)
{
struct timespec now = current_kernel_time();
return timespec_trunc(now, sb->s_time_gran);
}
We can surely do a little better than this, independent of the
conversion in Deepa's patch set.
> So for 32-bit code generation, we *may* want to introduce a new model of doing
>
> set_inode_time(inode, ATTR_ATIME | ATTR_MTIME);
>
> which basically just does
>
> inode->i_atime = inode->i_mtime = current_time(inode);
>
> but with a much easier calling convention on 32-bit architectures.
>
> But that is entirely orthogonal to this patch-set, and should be seen
> as a separate issue.
I've played around with that, but found it hard to avoid going
through memory other than going all the way to the tk_xtime()
access to copy both tk->xtime_sec and the nanoseconds into
the inode fields.
Without that, the set_inode_time() implementation ends up
being more expensive than
inode->i_atime = inode->i_ctime = inode->i_mtime = current_time(inode);
because we still copy through the stack but also have
a couple of conditional branches that we don't have at the
moment.
At the moment, the triple assignment becomes (here on ARM)
c: 4668 mov r0, sp
12: f7ff fffe bl 0 <current_kernel_time64>
3e: f107 0520 add.w r5, r7, #32
12: R_ARM_THM_CALL current_kernel_time64
16: f106 0410 add.w r4, r6, #16
1a: e89d 000f ldmia.w sp, {r0, r1, r2, r3} # load from stack
1e: e885 000f stmia.w r5, {r0, r1, r2, r3} # store into i_atime
22: e884 000f stmia.w r4, {r0, r1, r2, r3} # i_ctime
26: e886 000f stmia.w r6, {r0, r1, r2, r3} # i_mtime
and a slightly more verbose version of the same thing on x86
(storing only 12 bytes instead of 16 is cheaper there, while
ARM does a store-multiple to copy the entire structure).
Arnd
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
[PATCH v2 10/24] fs: cifs: Replace CURRENT_TIME by current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
[PATCH v2 09/24] fs: udf: Replace CURRENT_TIME with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
Re: [Y2038] [PATCH v2 09/24] fs: udf: Replace CURRENT_TIME with current_time() Arnd Bergmann <arnd@arndb.de> - 2016-06-22 16:10 +0200
Re: [Y2038] [PATCH v2 09/24] fs: udf: Replace CURRENT_TIME with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-23 04:00 +0200
[PATCH v2 07/24] fs: ubifs: Replace CURRENT_TIME_SEC with current_time Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
Re: [PATCH v2 07/24] fs: ubifs: Replace CURRENT_TIME_SEC with current_time Arnd Bergmann <arnd@arndb.de> - 2016-06-22 15:50 +0200
[PATCH v2 01/24] vfs: Add current_time() api Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
[PATCH v2 06/24] fs: ext4: Use current_time() for inode timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:30 +0200
Re: [PATCH v2 06/24] fs: ext4: Use current_time() for inode timestamps Arnd Bergmann <arnd@arndb.de> - 2016-06-22 15:40 +0200
[PATCH v2 11/24] fs: cifs: Replace CURRENT_TIME with ktime_get_real_ts() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
[PATCH v2 05/24] fs: jfs: Replace CURRENT_TIME_SEC by current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
Re: [Jfs-discussion] [PATCH v2 05/24] fs: jfs: Replace CURRENT_TIME_SEC by current_time() Dave Kleikamp <dave.kleikamp@oracle.com> - 2016-06-20 21:20 +0200
[PATCH v2 24/24] time: Delete current_fs_time() function Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
[PATCH v2 23/24] time: Delete CURRENT_TIME_SEC and CURRENT_TIME macro Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
Re: [PATCH v2 23/24] time: Delete CURRENT_TIME_SEC and CURRENT_TIME macro Arnd Bergmann <arnd@arndb.de> - 2016-06-22 17:50 +0200
[PATCH v2 08/24] fs: btrfs: Use ktime_get_real_ts for root ctime Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
Re: [PATCH v2 08/24] fs: btrfs: Use ktime_get_real_ts for root ctime David Sterba <dsterba@suse.cz> - 2016-06-20 11:50 +0200
[PATCH v2 04/24] fs: Replace current_fs_time() with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:40 +0200
[PATCH v2 18/24] fs: nfs: Make nfs boot time y2038 safe Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:50 +0200
[PATCH v2 16/24] fs: ocfs2: Replace CURRENT_TIME with ktime_get_real_seconds() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:50 +0200
[PATCH v2 22/24] fs: ceph: Replace current_fs_time for request stamp Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:50 +0200
[PATCH v2 17/24] audit: Use timespec64 to represent audit timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 02:50 +0200
Re: [PATCH v2 17/24] audit: Use timespec64 to represent audit timestamps Richard Guy Briggs <rgb@redhat.com> - 2016-06-20 17:20 +0200
[PATCH v2 19/24] fnic: Use time64_t to represent trace timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:30 +0200
Re: [PATCH v2 19/24] fnic: Use time64_t to represent trace timestamps Arnd Bergmann <arnd@arndb.de> - 2016-06-22 16:10 +0200
Re: [PATCH v2 19/24] fnic: Use time64_t to represent trace timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-23 04:00 +0200
[PATCH v2 13/24] fs: f2fs: Use ktime_get_real_seconds for sit_info times Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:30 +0200
[PATCH v2 14/24] drivers: staging: lustre: Replace CURRENT_TIME with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:40 +0200
[PATCH v2 15/24] fs: ocfs2: Use time64_t to represent orphan scan times Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:40 +0200
[PATCH v2 21/24] libceph: Replace CURRENT_TIME with ktime_get_real_ts Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:40 +0200
[PATCH v2 12/24] fs: cifs: Replace CURRENT_TIME by get_seconds Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 03:40 +0200
[PATCH v2 20/24] block: Replace CURRENT_TIME with ktime_get_real_ts Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 04:40 +0200
Re: [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-20 20:10 +0200
Re: [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Deepa Dinamani <deepa.kernel@gmail.com> - 2016-06-20 21:00 +0200
Re: [Y2038] [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Arnd Bergmann <arnd@arndb.de> - 2016-06-21 17:10 +0200
Re: [Y2038] [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Arnd Bergmann <arnd@arndb.de> - 2016-06-22 18:00 +0200
csiph-web