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Re: [PATCH] migration: Remove RDMA_UNREGISTRATION_EXAMPLE
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH] migration: Remove RDMA_UNREGISTRATION_EXAMPLE |
Date: |
Mon, 20 Jun 2022 18:30:11 +0100 |
User-agent: |
Mutt/2.2.5 (2022-05-16) |
* Juan Quintela (quintela@redhat.com) wrote:
> Nobody has ever showed up to unregister individual pages, and another
> set of patches written by Daniel P. Berrangé <berrange@redhat.com>
> just remove qemu_rdma_signal_unregister() function needed here.
>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> migration/rdma.c | 41 -----------------------------------------
> 1 file changed, 41 deletions(-)
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 672d1958a9..8504152f39 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1370,30 +1370,6 @@ const char *print_wrid(int wrid)
> return wrid_desc[wrid];
> }
>
> -/*
> - * RDMA requires memory registration (mlock/pinning), but this is not good
> for
> - * overcommitment.
> - *
> - * In preparation for the future where LRU information or workload-specific
> - * writable writable working set memory access behavior is available to QEMU
> - * it would be nice to have in place the ability to UN-register/UN-pin
> - * particular memory regions from the RDMA hardware when it is determine that
> - * those regions of memory will likely not be accessed again in the near
> future.
> - *
> - * While we do not yet have such information right now, the following
> - * compile-time option allows us to perform a non-optimized version of this
> - * behavior.
> - *
> - * By uncommenting this option, you will cause *all* RDMA transfers to be
> - * unregistered immediately after the transfer completes on both sides of the
> - * connection. This has no effect in 'rdma-pin-all' mode, only regular mode.
> - *
> - * This will have a terrible impact on migration performance, so until future
> - * workload information or LRU information is available, do not attempt to
> use
> - * this feature except for basic testing.
> - */
> -/* #define RDMA_UNREGISTRATION_EXAMPLE */
> -
> /*
> * Perform a non-optimized memory unregistration after every transfer
> * for demonstration purposes, only if pin-all is not requested.
> @@ -1571,18 +1547,6 @@ static uint64_t qemu_rdma_poll(RDMAContext *rdma,
> struct ibv_cq *cq,
> if (rdma->nb_sent > 0) {
> rdma->nb_sent--;
> }
> -
> - if (!rdma->pin_all) {
> - /*
> - * FYI: If one wanted to signal a specific chunk to be
> unregistered
> - * using LRU or workload-specific information, this is the
> function
> - * you would call to do so. That chunk would then get
> asynchronously
> - * unregistered later.
> - */
> -#ifdef RDMA_UNREGISTRATION_EXAMPLE
> - qemu_rdma_signal_unregister(rdma, index, chunk, wc.wr_id);
> -#endif
> - }
> } else {
> trace_qemu_rdma_poll_other(print_wrid(wr_id), wr_id, rdma->nb_sent);
> }
> @@ -2137,11 +2101,6 @@ retry:
>
> chunk_end = ram_chunk_end(block, chunk + chunks);
>
> - if (!rdma->pin_all) {
> -#ifdef RDMA_UNREGISTRATION_EXAMPLE
> - qemu_rdma_unregister_waiting(rdma);
> -#endif
> - }
>
> while (test_bit(chunk, block->transit_bitmap)) {
> (void)count;
> --
> 2.35.3
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK