Messages in this thread | | | Date | Mon, 13 Oct 2008 15:17:52 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 1/4] seq_file: don't call bitmap_scnprintf_len() |
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Alexey Dobriyan wrote: > On Sun, Oct 12, 2008 at 05:29:17PM +0800, Lai Jiangshan wrote: >> "m->count + len < m->size" is true commonly, so bitmap_scnprintf() >> is commonly called. this fix saves a call to bitmap_scnprintf_len(). > > This saves a call if seq buffer is already full which is not a common > situation, so you're optimising for rare situations and adding branch > for common ones.
Hi Alexey
I think this saves a call if seq buffer is _not_ full after called.
since calling bitmap_scnprintf() is the common situation. so we use the return value of bitmap_scnprintf() instead of bitmap_scnprintf_len().
In old code bitmap_scnprintf_len() and bitmap_scnprintf() must be called commonly.
Thanks Lai.
> >> --- a/fs/seq_file.c >> +++ b/fs/seq_file.c >> @@ -452,17 +452,18 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc) >> >> int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits) >> { >> - size_t len = bitmap_scnprintf_len(nr_bits); >> - >> - if (m->count + len < m->size) { >> - bitmap_scnprintf(m->buf + m->count, m->size - m->count, >> - bits, nr_bits); >> - m->count += len; >> - return 0; >> + if (m->count < m->size) { >> + int len = bitmap_scnprintf(m->buf + m->count, >> + m->size - m->count, bits, nr_bits); >> + if (m->count + len < m->size) { >> + m->count += len; >> + return 0; >> + } >> } >> m->count = m->size; >> return -1; >> } >> +EXPORT_SYMBOL(seq_bitmap); > > Modular users, where are they? > > >
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