From 0e6d6ec02f867fe8d1f785312b7343b21052322f Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Wed, 12 Mar 2014 10:41:32 +0100 Subject: [PATCH 1/2] drm/ttm: Work around performance regression with VM_PFNMAP A performance regression was introduced in TTM in linux 3.13 when we started using VM_PFNMAP for shared mappings. In theory this should've been faster due to less page book-keeping but it appears like VM_PFNMAP + x86 PAT + write-combine is a particularly cpu-hungry combination, as seen by largely increased cpu-usage on r200 GL video playback. Until we've sorted out why, revert to always use VM_MIXEDMAP. Reference: freedesktop.org bugzilla bug #75719 Reported-and-tested-by: Acked-by: Alex Deucher Signed-off-by: Thomas Hellstrom Cc: stable@vger.kernel.org --- drivers/gpu/drm/ttm/ttm_bo_vm.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index 801231c9ae48..0ce48e5a9cb4 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -339,11 +339,13 @@ int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma, vma->vm_private_data = bo; /* - * PFNMAP is faster than MIXEDMAP due to reduced page - * administration. So use MIXEDMAP only if private VMA, where - * we need to support COW. + * We'd like to use VM_PFNMAP on shared mappings, where + * (vma->vm_flags & VM_SHARED) != 0, for performance reasons, + * but for some reason VM_PFNMAP + x86 PAT + write-combine is very + * bad for performance. Until that has been sorted out, use + * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719 */ - vma->vm_flags |= (vma->vm_flags & VM_SHARED) ? VM_PFNMAP : VM_MIXEDMAP; + vma->vm_flags |= VM_MIXEDMAP; vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP; return 0; out_unref: @@ -359,7 +361,7 @@ int ttm_fbdev_mmap(struct vm_area_struct *vma, struct ttm_buffer_object *bo) vma->vm_ops = &ttm_bo_vm_ops; vma->vm_private_data = ttm_bo_reference(bo); - vma->vm_flags |= (vma->vm_flags & VM_SHARED) ? VM_PFNMAP : VM_MIXEDMAP; + vma->vm_flags |= VM_MIXEDMAP; vma->vm_flags |= VM_IO | VM_DONTEXPAND; return 0; } From 9ef7506f7eff3fc42724269f62e30164c141661f Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Wed, 12 Mar 2014 10:59:37 -0400 Subject: [PATCH 2/2] drm/ttm: don't oops if no invalidate_caches() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A few of the simpler TTM drivers (cirrus, ast, mgag200) do not implement this function. Yet can end up somehow with an evicted bo: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 16e761067 PUD 16e6cf067 PMD 0 Oops: 0010 [#1] SMP Modules linked in: bnep bluetooth rfkill fuse ip6t_rpfilter ip6t_REJECT ipt_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw iptable_filter ip_tables sg btrfs zlib_deflate raid6_pq xor dm_queue_length iTCO_wdt iTCO_vendor_support coretemp kvm dcdbas dm_service_time microcode serio_raw pcspkr lpc_ich mfd_core i7core_edac edac_core ses enclosure ipmi_si ipmi_msghandler shpchp acpi_power_meter mperf nfsd auth_rpcgss nfs_acl lockd uinput sunrpc dm_multipath xfs libcrc32c ata_generic pata_acpi sr_mod cdrom sd_mod usb_storage mgag200 syscopyarea sysfillrect sysimgblt i2c_algo_bit lpfc drm_kms_helper ttm crc32c_intel ata_piix bfa drm ixgbe libata i2c_core mdio crc_t10dif ptp crct10dif_common pps_core scsi_transport_fc dca scsi_tgt megaraid_sas bnx2 dm_mirror dm_region_hash dm_log dm_mod CPU: 16 PID: 2572 Comm: X Not tainted 3.10.0-86.el7.x86_64 #1 Hardware name: Dell Inc. PowerEdge R810/0H235N, BIOS 0.3.0 11/14/2009 task: ffff8801799dabc0 ti: ffff88016c884000 task.ti: ffff88016c884000 RIP: 0010:[<0000000000000000>] [< (null)>] (null) RSP: 0018:ffff88016c885ad8 EFLAGS: 00010202 RAX: ffffffffa04e94c0 RBX: ffff880178937a20 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000240004 RDI: ffff880178937a00 RBP: ffff88016c885b60 R08: 00000000000171a0 R09: ffff88007cf171a0 R10: ffffea0005842540 R11: ffffffff810487b9 R12: ffff880178937b30 R13: ffff880178937a00 R14: ffff88016c885b78 R15: ffff880179929400 FS: 00007f81ba2ef980(0000) GS:ffff88007cf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000016e763000 CR4: 00000000000007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Stack: ffffffffa0306fae ffff8801799295c0 0000000000260004 0000000000000001 ffff88016c885b60 ffffffffa0307669 00ff88007cf17738 ffff88017cf17700 ffff880178937a00 ffff880100000000 ffff880100000000 0000000079929400 Call Trace: [] ? ttm_bo_handle_move_mem+0x54e/0x5b0 [ttm] [] ? ttm_bo_mem_space+0x169/0x340 [ttm] [] ttm_bo_move_buffer+0x117/0x130 [ttm] [] ? perf_event_init_context+0x141/0x220 [] ttm_bo_validate+0xc1/0x130 [ttm] [] mgag200_bo_pin+0x87/0xc0 [mgag200] [] mga_crtc_cursor_set+0x474/0xbb0 [mgag200] [] ? __mem_cgroup_commit_charge+0x152/0x3b0 [] ? mutex_lock+0x12/0x2f [] drm_mode_cursor_common+0x123/0x170 [drm] [] drm_mode_cursor_ioctl+0x41/0x50 [drm] [] drm_ioctl+0x502/0x630 [drm] [] ? __do_page_fault+0x1f4/0x510 [] ? __restore_xstate_sig+0x218/0x4f0 [] do_vfs_ioctl+0x2e5/0x4d0 [] ? file_has_perm+0x8e/0xa0 [] SyS_ioctl+0x81/0xa0 [] system_call_fastpath+0x16/0x1b Code: Bad RIP value. RIP [< (null)>] (null) RSP CR2: 0000000000000000 Signed-off-by: Rob Clark Reviewed-by: Jérôme Glisse Reviewed-by: Thomas Hellstrom Cc: stable@vger.kernel.org --- drivers/gpu/drm/ttm/ttm_bo.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index a06651309388..214b7992a3aa 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -351,9 +351,11 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo, moved: if (bo->evicted) { - ret = bdev->driver->invalidate_caches(bdev, bo->mem.placement); - if (ret) - pr_err("Can not flush read caches\n"); + if (bdev->driver->invalidate_caches) { + ret = bdev->driver->invalidate_caches(bdev, bo->mem.placement); + if (ret) + pr_err("Can not flush read caches\n"); + } bo->evicted = false; }