From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> Subject: Re: [PATCH] Latest dm-userspace, with memory reclaim Date: Sun, 10 Sep 2006 22:34:39 +0900 > From: Dan Smith <danms@xxxxxxxxxx> > Subject: [PATCH] Latest dm-userspace, with memory reclaim > Date: Tue, 29 Aug 2006 09:54:38 -0700 > > > This is the latest version of dm-userspace. I have added a > > (configurable) limit on the number of remap objects the kernel will > > maintain in memory before re-using old ones. > > > > I think it may be beneficial to have a soft and a hard limit on this, > > to allow allocation to be done if no remaps can be re-used at a given > > point (up to the hard limit). Comments appreciated. > > How about removing the remap object mechanism? > > You said that the remap object mechanism improves the performance by > avoiding contacting user space for every requests. However, as you > see, Xen blktap (contacting user space for every requests) and blkback > (doing I/O in kernel) performances are comparable. dm-userspace's poor > performance of user space access is due to ioctl, an inefficient > interface. The blktap uses shared ring buffer between kernel and user > space, which enables us to batch multiple requests without data > copies. > > Here's a patch to remove the remap object mechanism and add replaced > ioctl with ring buffer. The mailing list removed my patch for some reasons. So I uploaded the patch too: http://www.kernel.org/pub/linux/kernel/people/tomo/dmu/ringbuf.patch -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
