Performance: cache the backend pages pointer in context

[lttng-ust.git] / libringbuffer / backend.h

diff --git a/libringbuffer/backend.h b/libringbuffer/backend.h
index 2dec003883c7536ce3912b94b4a9987cc5d3b777..1364d383f4006b7c9db851aeb0813d8e55cbd2b6 100644 (file)
--- a/libringbuffer/backend.h
+++ b/libringbuffer/backend.h
@@ -76,36 +76,24 @@ void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config
                           struct lttng_ust_lib_ring_buffer_ctx *ctx,
                           const void *src, size_t len)
 {
-       struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
        struct channel_backend *chanb = &ctx->chan->backend;
        struct lttng_ust_shm_handle *handle = ctx->handle;
-       size_t sbidx;
        size_t offset = ctx->buf_offset;
-       struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
-       unsigned long sb_bindex, id;
        struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
        void *p;
 
        if (caa_unlikely(!len))
                return;
-       offset &= chanb->buf_size - 1;
-       sbidx = offset >> chanb->subbuf_size_order;
-       id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
-       sb_bindex = subbuffer_id_get_index(config, id);
-       rpages = shmp_index(handle, bufb->array, sb_bindex);
-       if (caa_unlikely(!rpages))
-               return;
-       CHAN_WARN_ON(ctx->chan,
-                    config->mode == RING_BUFFER_OVERWRITE
-                    && subbuffer_id_is_noref(config, id));
        /*
         * Underlying layer should never ask for writes across
         * subbuffers.
         */
-       CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
-       backend_pages = shmp(handle, rpages->shmp);
-       if (caa_unlikely(!backend_pages))
-               return;
+       CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
+       backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+       if (caa_unlikely(!backend_pages)) {
+               if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
+                       return;
+       }
        p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
        if (caa_unlikely(!p))
                return;
@@ -159,47 +147,46 @@ void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *confi
                           struct lttng_ust_lib_ring_buffer_ctx *ctx,
                           const char *src, size_t len, int pad)
 {
-       struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
        struct channel_backend *chanb = &ctx->chan->backend;
        struct lttng_ust_shm_handle *handle = ctx->handle;
-       size_t sbidx, count;
+       size_t count;
        size_t offset = ctx->buf_offset;
-       struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
-       unsigned long sb_bindex, id;
+       struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
+       void *p;
 
        if (caa_unlikely(!len))
                return;
-       offset &= chanb->buf_size - 1;
-       sbidx = offset >> chanb->subbuf_size_order;
-       id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
-       sb_bindex = subbuffer_id_get_index(config, id);
-       rpages = shmp_index(handle, bufb->array, sb_bindex);
-       CHAN_WARN_ON(ctx->chan,
-                    config->mode == RING_BUFFER_OVERWRITE
-                    && subbuffer_id_is_noref(config, id));
        /*
         * Underlying layer should never ask for writes across
         * subbuffers.
         */
-       CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
-       count = lib_ring_buffer_do_strcpy(config,
-                       shmp_index(handle, shmp(handle, rpages->shmp)->p,
-                               offset & (chanb->subbuf_size - 1)),
-                       src, len - 1);
+       CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
+       backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
+       if (caa_unlikely(!backend_pages)) {
+               if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
+                       return;
+       }
+       p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
+       if (caa_unlikely(!p))
+               return;
+
+       count = lib_ring_buffer_do_strcpy(config, p, src, len - 1);
        offset += count;
        /* Padding */
        if (caa_unlikely(count < len - 1)) {
                size_t pad_len = len - 1 - count;
 
-               lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
-                               offset & (chanb->subbuf_size - 1)),
-                       pad, pad_len);
+               p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
+               if (caa_unlikely(!p))
+                       return;
+               lib_ring_buffer_do_memset(p, pad, pad_len);
                offset += pad_len;
        }
        /* Final '\0' */
-       lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
-                               offset & (chanb->subbuf_size - 1)),
-                       '\0', 1);
+       p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
+       if (caa_unlikely(!p))
+               return;
+       lib_ring_buffer_do_memset(p, '\0', 1);
        ctx->buf_offset += len;
 }