96cc493c74
resolves: RHEL-88543 Remove usage of nbdkit-cacheextents-filter resolves: RHEL-88857 Print better mountpoint stats in debug output resolves: RHEL-88861 Add virt-v2v -io vddk-noextents=true so we can test noextents resolves: RHEL-88863 Remove several ancient, deprecated options resolves: RHEL-88866
98 lines
3.5 KiB
Diff
98 lines
3.5 KiB
Diff
From 212beda84cd9366b65f73d71664f1a2aaeafc9f8 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Tue, 29 Apr 2025 10:29:08 +0100
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Subject: [PATCH] input: Remove usage of nbdkit-cacheextents-filter
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The caching in this filter
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(https://libguestfs.org/nbdkit-cacheextents-filter.1.html) is very
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simple. It is basically designed so that if a client asks for one
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extent at a time (using the NBD flag NBD_CMD_FLAG_REQ_ONE) then we ask
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for all the extents that the underlying plugin will give us, and cache
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those. However only a single contiguous set of extents is cached, and
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any non-contiguous read will blow away the cache.
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This was designed entirely to work around the buggy behaviour of
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'qemu-img convert', which makes lots of req_one requests like this.
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nbdcopy works completely differently, and doesn't have this problem.
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nbdcopy also reads non-contiguous stretches of the input from multiple
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threads. The filter in this case isn't effective (it doesn't do
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anything bad since nbdcopy doesn't use the req_one flag).
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In addition, the infamously slow QueryAllocatedBlocks API is only
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called from the copy stage, and never (or maybe almost never) from the
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conversion stage, so nothing that qemu does could justify caching
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extents.
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As this filter is essentially useless with current virt-v2v / nbdcopy,
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remove its use completely.
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(cherry picked from commit 48c4ce8e6cf6f1c390a48245ef0f99233f80cfe8)
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---
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README | 1 -
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input/nbdkit_curl.ml | 5 -----
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input/nbdkit_ssh.ml | 5 -----
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input/nbdkit_vddk.ml | 5 -----
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4 files changed, 16 deletions(-)
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diff --git a/README b/README
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index 4354754f..e4785166 100644
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--- a/README
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+++ b/README
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@@ -69,7 +69,6 @@ REQUIREMENTS
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+ nbdkit-ssh-plugin
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+ nbdkit-vddk-plugin
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- + nbdkit-cacheextents-filter
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+ nbdkit-cow-filter
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+ nbdkit-multi-conn-filter
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+ nbdkit-rate-filter
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diff --git a/input/nbdkit_curl.ml b/input/nbdkit_curl.ml
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index 7e13c205..695f6d7c 100644
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--- a/input/nbdkit_curl.ml
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+++ b/input/nbdkit_curl.ml
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@@ -71,11 +71,6 @@ let create_curl ?bandwidth ?cookie_script ?cookie_script_renew ?cor
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*)
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Nbdkit.add_filter_if_available cmd "retry";
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- (* Caching extents speeds up qemu-img, especially its consecutive
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- * block_status requests with req_one=1.
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- *)
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- Nbdkit.add_filter_if_available cmd "cacheextents";
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-
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(* IMPORTANT! Add the COW filter. It must be furthest away
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* except for the rate filter.
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*)
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diff --git a/input/nbdkit_ssh.ml b/input/nbdkit_ssh.ml
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index 1a2d2b56..4aba74f3 100644
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--- a/input/nbdkit_ssh.ml
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+++ b/input/nbdkit_ssh.ml
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@@ -69,11 +69,6 @@ let create_ssh ?bandwidth ?cor ?(retry=true)
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if retry then
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Nbdkit.add_filter_if_available cmd "retry";
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- (* Caching extents speeds up qemu-img, especially its consecutive
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- * block_status requests with req_one=1.
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- *)
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- Nbdkit.add_filter_if_available cmd "cacheextents";
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-
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(* IMPORTANT! Add the COW filter. It must be furthest away
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* except for the rate filter.
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*)
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diff --git a/input/nbdkit_vddk.ml b/input/nbdkit_vddk.ml
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index 0cb45e89..b79c28cc 100644
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--- a/input/nbdkit_vddk.ml
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+++ b/input/nbdkit_vddk.ml
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@@ -140,11 +140,6 @@ See also the virt-v2v-input-vmware(1) manual.") libNN
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*)
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Nbdkit.add_filter_if_available cmd "retry";
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- (* Caching extents speeds up qemu-img, especially its consecutive
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- * block_status requests with req_one=1.
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- *)
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- Nbdkit.add_filter_if_available cmd "cacheextents";
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-
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(* Split very large requests to avoid out of memory errors on the
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* server. Since we're using this filter, also add minblock=512
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* although it will make no difference.
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