From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46463) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UPXSx-0006Ep-M3 for qemu-devel@nongnu.org; Tue, 09 Apr 2013 08:16:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UPXSs-0000dJ-Up for qemu-devel@nongnu.org; Tue, 09 Apr 2013 08:15:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9248) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UPXSs-0000dC-J9 for qemu-devel@nongnu.org; Tue, 09 Apr 2013 08:15:54 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r39CFro0012806 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 9 Apr 2013 08:15:54 -0400 From: Juan Quintela In-Reply-To: <5164013A.6030407@redhat.com> (Paolo Bonzini's message of "Tue, 09 Apr 2013 13:53:30 +0200") References: <1365420597-5506-1-git-send-email-pbonzini@redhat.com> <1365420597-5506-5-git-send-email-pbonzini@redhat.com> <874nfgdj51.fsf@elfo.elfo> <5164013A.6030407@redhat.com> Date: Tue, 09 Apr 2013 14:16:00 +0200 Message-ID: <87zjx7dhmn.fsf@elfo.elfo> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 4/4] migration: simplify writev vs. non-writev logic Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, owasserm@redhat.com, qemu-devel@nongnu.org Paolo Bonzini wrote: > 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? We can rename the function. I agree with that. > > 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). Right now, it is important because all the integer types are sent as callas to qemu_put_byte(), but Orit had a patch to rewrote those using qemu_put_buffer() dirrectly, and then we don't use so many qemu_put_byte()'s anymore. Later, Juan.