| Message ID | 20180117082050.25406-1-avagin@openvz.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jan 17, 2018 at 12:20:50AM -0800, Andrei Vagin wrote: > + * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v) No, it is not. Scratch "0x". > +void seq_put_hex_ll(struct seq_file *m, const char *delimiter, > + unsigned long long v, int width) I understand that "unsigned long long" mimics decimal counterpart, but in thie case everything is "unsigned long" including ->vm_pgoff. Also, width should be unsigned for the common case of %08lx (and "len" too) > +{ > + int i, len; > + > + if (delimiter && delimiter[0]) { > + if (delimiter[1] == 0) > + seq_putc(m, delimiter[0]); > + else > + seq_puts(m, delimiter); > + } > + > + /* If x is 0, the result of __builtin_clzll is undefined */ > + if (v == 0) > + len = 1; > + else > + len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4; > + > + if (len < width) > + len = width; > + > + if (m->count + len > m->size) { > + seq_set_overflow(m); > + return; > + } > + > + for (i = len - 1; i >= 0; i--) { > + m->buf[m->count + i] = hex_asc[0xf & v]; > + v = v >> 4; > + } > + m->count += len; > +}
On Fri, Feb 09, 2018 at 04:48:47PM +0300, Alexey Dobriyan wrote: > On Wed, Jan 17, 2018 at 12:20:50AM -0800, Andrei Vagin wrote: > > + * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v) > > No, it is not. Scratch "0x". will fix > > > +void seq_put_hex_ll(struct seq_file *m, const char *delimiter, > > + unsigned long long v, int width) > > I understand that "unsigned long long" mimics decimal counterpart, > but in thie case everything is "unsigned long" including ->vm_pgoff. I've checked that the performance is the same for "unsigned long long" and "unsigned long". Do we have other reasons to use "unsigned long" rather than "unsigned long long"? > > Also, width should be unsigned for the common case of %08lx > (and "len" too) will fix Thank you for the review. > > > +{ > > + int i, len; > > +
On Fri, Feb 09, 2018 at 11:50:01PM -0800, Andrei Vagin wrote: > On Fri, Feb 09, 2018 at 04:48:47PM +0300, Alexey Dobriyan wrote: > > On Wed, Jan 17, 2018 at 12:20:50AM -0800, Andrei Vagin wrote: > > > + * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v) > > > > No, it is not. Scratch "0x". > > will fix > > > > > +void seq_put_hex_ll(struct seq_file *m, const char *delimiter, > > > + unsigned long long v, int width) > > > > I understand that "unsigned long long" mimics decimal counterpart, > > but in thie case everything is "unsigned long" including ->vm_pgoff. > > I've checked that the performance is the same for "unsigned long long" and > "unsigned long". Do we have other reasons to use "unsigned long" rather > than "unsigned long long"? On 32-bit those types are different. But I guess as seq_put_decimal is ull, it is worse to deviate.
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 339e4c1c044d..3a08685ef27c 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -282,15 +282,18 @@ static void show_vma_header_prefix(struct seq_file *m, dev_t dev, unsigned long ino) { seq_setwidth(m, 25 + sizeof(void *) * 6 - 1); - seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ", - start, - end, - flags & VM_READ ? 'r' : '-', - flags & VM_WRITE ? 'w' : '-', - flags & VM_EXEC ? 'x' : '-', - flags & VM_MAYSHARE ? 's' : 'p', - pgoff, - MAJOR(dev), MINOR(dev), ino); + seq_put_hex_ll(m, NULL, start, 8); + seq_put_hex_ll(m, "-", end, 8); + seq_putc(m, ' '); + seq_putc(m, flags & VM_READ ? 'r' : '-'); + seq_putc(m, flags & VM_WRITE ? 'w' : '-'); + seq_putc(m, flags & VM_EXEC ? 'x' : '-'); + seq_putc(m, flags & VM_MAYSHARE ? 's' : 'p'); + seq_put_hex_ll(m, " ", pgoff, 8); + seq_put_hex_ll(m, " ", MAJOR(dev), 2); + seq_put_hex_ll(m, ":", MINOR(dev), 2); + seq_put_decimal_ull(m, " ", ino); + seq_putc(m, ' '); } static void diff --git a/fs/seq_file.c b/fs/seq_file.c index bce089cc1771..d2885220ecf7 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -712,6 +712,51 @@ void seq_put_decimal_ull(struct seq_file *m, const char *delimiter, } EXPORT_SYMBOL(seq_put_decimal_ull); +/** + * seq_put_hex_ll - put a number in hexadecimal notation + * @m: seq_file identifying the buffer to which data should be written + * @delimiter: a string which is printed before the number + * @v: the number + * @width: a minimum field width + * + * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v) + * + * This routine is very quick when you show lots of numbers. + * In usual cases, it will be better to use seq_printf(). It's easier to read. + */ +void seq_put_hex_ll(struct seq_file *m, const char *delimiter, + unsigned long long v, int width) +{ + int i, len; + + if (delimiter && delimiter[0]) { + if (delimiter[1] == 0) + seq_putc(m, delimiter[0]); + else + seq_puts(m, delimiter); + } + + /* If x is 0, the result of __builtin_clzll is undefined */ + if (v == 0) + len = 1; + else + len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4; + + if (len < width) + len = width; + + if (m->count + len > m->size) { + seq_set_overflow(m); + return; + } + + for (i = len - 1; i >= 0; i--) { + m->buf[m->count + i] = hex_asc[0xf & v]; + v = v >> 4; + } + m->count += len; +} + void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num) { int len; diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 09c6e28746f9..53f238934d7f 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -121,6 +121,9 @@ void seq_puts(struct seq_file *m, const char *s); void seq_put_decimal_ull(struct seq_file *m, const char *delimiter, unsigned long long num); void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num); +void seq_put_hex_ll(struct seq_file *m, const char *delimiter, + unsigned long long v, int width); + void seq_escape(struct seq_file *m, const char *s, const char *esc); void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
seq_put_hex_ll() prints a number in hexadecimal notation and works faster than seq_printf(). == test.py num = 0 with open("/proc/1/maps") as f: while num < 10000 : data = f.read() f.seek(0, 0) num = num + 1 == == Before patch == $ time python test.py real 0m1.561s user 0m0.257s sys 0m1.302s == After patch == $ time python test.py real 0m0.986s user 0m0.279s sys 0m0.707s $ perf -g record python test.py: == Before patch == - 67.42% 2.82% python [kernel.kallsyms] [k] show_map_vma.isra.22 - 64.60% show_map_vma.isra.22 - 44.98% seq_printf - seq_vprintf - vsnprintf + 14.85% number + 12.22% format_decode 5.56% memcpy_erms + 15.06% seq_path + 4.42% seq_pad + 2.45% __GI___libc_read == After patch == - 47.35% 3.38% python [kernel.kallsyms] [k] show_map_vma.isra.23 - 43.97% show_map_vma.isra.23 + 20.84% seq_path - 15.73% show_vma_header_prefix 10.55% seq_put_hex_ll + 2.65% seq_put_decimal_ull 0.95% seq_putc + 6.96% seq_pad + 2.94% __GI___libc_read v2: don't create a separate function to print delimiter and a few fixes to make code more readable. Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrei Vagin <avagin@openvz.org> --- fs/proc/task_mmu.c | 21 ++++++++++++--------- fs/seq_file.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/seq_file.h | 3 +++ 3 files changed, 60 insertions(+), 9 deletions(-)