On Thu, Jul 28, 2016 at 03:30:09AM +0000, Li, Liang Z wrote: > > Subject: Re: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate > > process > > > > On Wed, Jul 27, 2016 at 09:03:21AM -0700, Dave Hansen wrote: > > > On 07/26/2016 06:23 PM, Liang Li wrote: > > > > + vb->pfn_limit = VIRTIO_BALLOON_PFNS_LIMIT; > > > > + vb->pfn_limit = min(vb->pfn_limit, get_max_pfn()); > > > > + vb->bmap_len = ALIGN(vb->pfn_limit, BITS_PER_LONG) / > > > > + BITS_PER_BYTE + 2 * sizeof(unsigned long); > > > > + hdr_len = sizeof(struct balloon_bmap_hdr); > > > > + vb->bmap_hdr = kzalloc(hdr_len + vb->bmap_len, GFP_KERNEL); > > > > > > This ends up doing a 1MB kmalloc() right? That seems a _bit_ big. > > > How big was the pfn buffer before? > > > > > > Yes I would limit this to 1G memory in a go, will result in a 32KByte > > bitmap. > > > > -- > > MST > > Limit to 1G is bad for the performance, I sent you the test result several > weeks ago. > > Paste it bellow: > ------------------------------------------------------------------------------------------------------------------------ > About the size of page bitmap, I have test the performance of filling the > balloon to 15GB with a > 16GB RAM VM. > > =============================== > 32K Byte (cover 1GB of RAM) > > Time spends on inflating: 2031ms > --------------------------------------------- > 64K Byte (cover 2GB of RAM) > > Time spends on inflating: 1507ms > -------------------------------------------- > 512K Byte (cover 16GB of RAM) > > Time spends on inflating: 1237ms > ================================ > > If possible, a big bitmap is better for performance. > > Liang
Earlier you said: a. allocating pages (6.5%) b. sending PFNs to host (68.3%) c. address translation (6.1%) d. madvise (19%) Here sending PFNs to host with 512K Byte map should be almost free. So is something else taking up the time? -- MST
