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Re: [Qemu-devel] [PATCH 4/4] migration: simplify writev vs. non-writev l
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 4/4] migration: simplify writev vs. non-writev logic |
Date: |
Tue, 09 Apr 2013 13:53:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 |
Il 09/04/2013 13:43, Juan Quintela ha scritto:
>> > @@ -687,12 +685,10 @@ void qemu_put_byte(QEMUFile *f, int v)
>> > f->bytes_xfer++;
>> > if (f->ops->writev_buffer) {
>> > add_to_iovec(f, f->buf + f->buf_index, 1);
>> > - f->buf_index++;
>> > - } else {
>> > - f->buf_index++;
>> > - if (f->buf_index == IO_BUF_SIZE) {
>> > - qemu_fflush(f);
>> > - }
>> > + }
>> > + f->buf_index++;
>> > + if (f->buf_index == IO_BUF_SIZE) {
>> > + qemu_fflush(f);
>> > }
>> > }
> If you follow my advice of moving the call to add_to_iovec() you get
> this one simplified and only one place to do this.
Moving what call? The apparent complication is because the old logic
was a bit more involute than necessary. If you look at the code after
the patches, not the patches themselves, you'll see for yourself.
The logic now is:
add byte
if using iovs
add byte to iov list
if buffer full
flush
add_to_iovec has no business checking the buffer. Why should
qemu_put_buffer_async() check the buffer?
The duplication between qemu_put_byte and qemu_put_buffer is a different
topic. I think it's acceptable in the name of performance, but perhaps
you can just call qemu_put_buffer(f, &c, 1).
Paolo
- [Qemu-devel] [PATCH 3/4] migration: drop is_write complications, (continued)
[Qemu-devel] [PATCH 2/4] migration: use a single I/O operation when writev_buffer is not defined, Paolo Bonzini, 2013/04/08
[Qemu-devel] [PATCH 4/4] migration: simplify writev vs. non-writev logic, Paolo Bonzini, 2013/04/08
Re: [Qemu-devel] [PATCH 0/4] QEMUFile improvements and simplifications, Juan Quintela, 2013/04/09
Re: [Qemu-devel] [PATCH 0/4] QEMUFile improvements and simplifications, Liuji (Jeremy), 2013/04/10