Minor edits around Optimization

docs/topics/optimize.rst

@@ -21,11 +21,12 @@ For broad crawls, consider these adjustments:
 
 -   .. _broad-crawls-concurrency:
 
-    Increase global concurrency:
+    Increase the global concurrency:
 
-    -   Set :setting:`CONCURRENT_REQUESTS` as close to “number of target
-        domains” times :setting:`CONCURRENT_REQUESTS_PER_DOMAIN` (e.g. 80 for
-        10 domains) as your CPU and memory allow.
+    -   Set :setting:`CONCURRENT_REQUESTS` as close to
+        :setting:`CONCURRENT_REQUESTS_PER_DOMAIN` × [number of target domains]
+        (e.g. 8 × 10 domains = 80 concurrent requests) as your CPU and memory
+        allow.
 
     -   Increase :setting:`SCRAPER_SLOT_MAX_ACTIVE_SIZE` when increasing
         :setting:`CONCURRENT_REQUESTS` stops making a difference.
@@ -87,8 +88,9 @@ Lowering memory usage
         :attr:`~scrapy.Request.callback` cannot yield additional
         requests.
 
-    -   If you have many :ref:`start requests <start-requests>`, use :ref:`lazy
-        <start-requests-lazy>` or :ref:`idle <start-requests-idle>` scheduling.
+    -   If you have multiple :ref:`start requests <start-requests>`, consider
+        :ref:`lazy <start-requests-lazy>` or :ref:`idle <start-requests-idle>`
+        scheduling.
 
     -   Set :setting:`JOBDIR` to offload all scheduled requests to disk.
 

docs/topics/request-response.rst

@@ -20,6 +20,7 @@ functionality not required in the base classes. These are described
 below in :ref:`topics-request-response-ref-request-subclasses` and
 :ref:`topics-request-response-ref-response-subclasses`.
 
+.. _request:
 
 Request objects
 ===============

docs/topics/spiders.rst

@@ -369,13 +369,16 @@ See `Scrapyd documentation`_.
 Start requests
 ==============
 
-**Start requests** are the requests yielded by the :meth:`~scrapy.Spider.start`
-method of a spider.
+**Start requests** are the :ref:`requests <request>` that serve as a starting
+point for a spider.
 
-By default, Scrapy does not try to send :meth:`~scrapy.Spider.start` requests
-in order. Instead, it prioritizes reaching :setting:`CONCURRENT_REQUESTS` and
-:ref:`scheduling <topics-scheduler>` start requests. However, you can change
-that.
+They are yielded by the :meth:`~scrapy.Spider.start` method, and may be
+modified by :ref:`spider middlewares <topics-spider-middleware>`.
+
+They are not necessarily the *first* requests sent, and may not be sent in
+order; reaching :setting:`CONCURRENT_REQUESTS` and :ref:`scheduling
+<topics-scheduler>` start requests is prioritized by default. But you can
+change that.
 
 ..
     The request send order when all start requests and callback requests have
@@ -454,8 +457,8 @@ is reached, start requests are removed from the scheduler immediately after
 they are scheduled.
 
 If you do not yield the highest-priority start requests first, and you want
-request priorities to be respected since the first request, pause the scheduler
-while yielding your start requests:
+request priorities to be respected since the very first request, pause the
+:ref:`scheduler <topics-scheduler>` while yielding your start requests:
 
 .. code-block:: python