Hi Ming, What I need is that always get contiguous pages in one bvec. Maybe currently it's hard to satisfy this requirement. About huge pages, I know the userspace processes could use huge pages that kernel reserved. Could bio/block layer support use huge pages? Thanks again for your help. Ming Lei <ming.lei@xxxxxxxxxx> 于2020年3月17日周二 下午6:27写道: > > On Tue, Mar 17, 2020 at 04:19:44PM +0800, Feng Li wrote: > > Thanks. > > Sometimes when I observe multipage bvec on 5.3.7-301.fc31.x86_64. > > This log is from Qemu virtio-blk. > > > > ========= size: 262144, iovcnt: 2 > > 0: size: 229376 addr: 0x7fff6a7c8000 > > 1: size: 32768 addr: 0x7fff64c00000 > > ========= size: 262144, iovcnt: 2 > > 0: size: 229376 addr: 0x7fff6a7c8000 > > 1: size: 32768 addr: 0x7fff64c00000 > > Then it is working. > > > > > I also tested on 5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64. > > And observe 64 iovcnt. > > ========= size: 262144, iovcnt: 64 > > 0: size: 4096 addr: 0x7fffb5ece000 > > 1: size: 4096 addr: 0x7fffb5ecd000 > > ... > > 63: size: 4096 addr: 0x7fff8baec000 > > > > So I think this is a common issue of the upstream kernel, from 5.3 to 5.6. > > As I mentioned before, it is because the pages aren't contiguous > physically. > > If you enable hugepage, you will see lot of pages in one single bvec. > > > > > BTW, I have used your script on 5.3.7-301.fc31.x86_64, it works well. > > However, when updating to kernel 5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64. > > It complains: > > > > root@192.168.19.239 16:57:23 ~ $ ./bvec_avg_pages.py > > In file included from /virtual/main.c:2: > > In file included from > > /lib/modules/5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64/build/include/uapi/linux/ptrace.h:142: > > In file included from > > /lib/modules/5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64/build/arch/x86/include/asm/ptrace.h:5: > > /lib/modules/5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64/build/arch/x86/include/asm/segment.h:266:2: > > error: expected '(' after 'asm' > > alternative_io ("lsl %[seg],%[p]", > > It can be workaround by commenting the following line in > /lib/modules/5.6.0-0.rc6.git0.1.vanilla.knurd.1.fc31.x86_64/build/include/generated/autoconf.h: > > #define CONFIG_CC_HAS_ASM_INLINE 1 > > > Thanks, > Ming >